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IMAT 2024 Worked Solutions

Deep dive into the 2024 exam questions and analysis. Explore detailed worked solutions and key concept breakdowns.

1
1. Who is the author of the famous novel To the Lighthouse?
A)
Virginia Wolf
B)
Mary Shelley
C)
Jane Austen
D)
Emily Dickinson
E)
Agatha Christie
Theme: Literary Knowledge
Explanation:
The question asks to identify the author of the novel To the Lighthouse.
- A) Virginia Woolf: She is the correct author. To the Lighthouse was published in 1927 and is a landmark of modernist literature.
Why other options are incorrect:
- B) Mary Shelley: Famous for Frankenstein.
- C) Jane Austen: Famous for novels like Pride and Prejudice and Sense and Sensibility.
- D) Emily Dickinson: Was a renowned American poet, not primarily a novelist.
- E) Agatha Christie: Famous for her detective novels, particularly those featuring Hercile Poirot and Miss Marple.
Answer:→A) Virginia Wolf
2
2. Based on historical records, we can say that many ancient societies devised symbols to represent
numbers and solutions to mathematical problems.
Although thinkers began to take the first steps
towards mathematics early on, it can be asserted that only with Greek civilisation did this discipline
acquire the abstract and general characteristics that render it distinct and render it a unique science.
It is noteworthy that mathematics evolved into an abstract and general science at a deliberate pace.
Documents from pre-Greek civilisations indicate that solutions to mathematical problems were
confined to specific, tangible cases.
These documents convey the impression that mathematical
concepts were communicated sporadically and non-methodically (occasionally even fortuitously),
and were treated as useful information geared towards practical outcomes.
MANARA, LUCCHINI Momenti del pensiero matematico - Mursia
Which of the following CANNOT be inferred from the text?
A)
Since antiquity, mathematics has been characterized by abstractness and generality.
B)
In antiquity, mathematical notions were not communicated in a methodical manner.
C)
Symbols representing numbers had already been adopted in antiquity.
D)
In antiquity, mathematical notions were geared towards practical outcomes.
E)
The evolution of mathematics has been an extremely slow process.
Theme: Reading Comprehension (Inference)
Explanation:
The question asks which statement cannot be inferred from the provided text.
- A) Since antiquity, mathematics has been characterized by abstractness and generality: This statement CANNOT be inferred. The text explicitly contradicts this by stating "...only with Greek civilisation did this discipline acquire the abstract and general characteristics...". Before that, solutions were "confined to specific, tangible cases".
Why other options can be inferred:
- B): The text states concepts were "communicated sporadically and non-methodically".
- C): The text opens by saying "many ancient societies devised symbols to represent numbers".
- D): The text states concepts were "geared towards practical outcomes".
- E): The text mentions it evolved at a "deliberate pace", and this option is presented as a valid inference in the test.
Answer:→A) Since antiquity, mathematics has been characterized by abstractness and generality.
3
3. The Hundred Years' War was principally a conflict between which of the following kingdoms?
A)
The Kingdom of France and the Kingdom of England
B)
The Kingdom of Aragon and the Kingdom of France
C)
The Kingdom of Aragon and The Kingdom of Castile
D)
The Kingdom of Castile and the Kingdom of Portugal
E)
The Kingdom of England and the Kingdom of Portugal
Theme: Historical Knowledge
Explanation:
This is a direct question about a major historical event.
- A) The Kingdom of France and the Kingdom of England: This is the correct answer. The Hundred Years' War (lasting from 1337 to 1453) was a prolonged series of conflicts fought between these two kingdoms over the right to rule the Kingdom of France.
Answer:→A) The Kingdom of France and the Kingdom of England
4
4. In which of the following is the verb passive?
A)
The deeds of Aeneas were sung by Virgil.
B)
Many students read Greek tragedies in high school.
C)
In the Gallic Wars, Julius Caesar described in detail his military campaign to conquer Gaul.
D)
In one of his works, Plato associates solid forms to the four elements: octahedron to air, tetrahedron to fire, cube to earth, and icosahedron to water.
E)
In the Iliad, Homer sings the deeds of the Pelide Achilles.
Theme: Grammar (Passive Voice)
Explanation:
The passive voice is a grammatical construction where the subject of the sentence receives the action, rather than performing it. The structure is typically [Subject] + [form of 'to be'] + [Past Participle] + [by Agent].
- A) The deeds of Aeneas were sung by Virgil: This fits the passive voice structure. The subject ("The deeds of Aeneas") is receiving the action ("were sung"). The agent performing the action ("Virgil") is introduced by "by".
Why other options are incorrect (Active Voice):
- B): "Many students" (subject) "read" (verb). Students perform the action.
- C): "Julius Caesar" (subject) "described" (verb). Caesar performs the action.
- D): "Plato" (subject) "associates" (verb). Plato performs the action.
- E): "Homer" (subject) "sings" (verb). Homer performs the action.
Answer:→A) The deeds of Aeneas were sung by Virgil.
5
5. The following table shows the results of a test:
                                                                                                                                                                                                               
Mark
Frequency
0
1
           
| 1 | 4 |
| 2 | 4 |
| 3 | 6 |
| 4 | 2 |
| 5 | 1 |
| 6 | 1 |
| 7 | 2 |
| 8 | 2 |
| 9 | 1 |
| 10 | 0 |
To pass the test, a mark of higher than 5 is needed. What percentage of the candidates passed the test?
A)
25%
B)
24%
C)
20%
D)
30%
E)
50%
Theme: Data Interpretation (Table)
Explanation:
The problem requires calculating the percentage of candidates who passed, based on the provided frequency table.
1. Find the total number of candidates:
Sum the frequencies for all marks (0 to 10).
Total = 1 (mark 0) + 4 (mark 1) + 4 (mark 2) + 6 (mark 3) + 2 (mark 4) + 1 (mark 5) + 1 (mark 6) + 2 (mark 7) + 2 (mark 8) + 1 (mark 9) + 0 (mark 10)
Total = 24 candidates.
2. Find the number of candidates who passed:
The condition to pass is a mark "higher than 5" (i.e., 6, 7, 8, 9, or 10).
Passed = (Frequency of 6) + (Frequency of 7) + (Frequency of 8) + (Frequency of 9) + (Frequency of 10)
Passed = 1 + 2 + 2 + 1 + 0 = 6 candidates.
3. Calculate the percentage:
Percentage = $\frac{\text{Passed}}{\text{Total}} \times 100$
Percentage = $\frac{6}{24} \times 100 = 0.25 \times 100 = 25\%$.
Answer:→A) 25%
6
6. Shelly is one of 1500 participants in a Latin contest. 12% of the participants will receive as a prize either a silver-plated or gold-plated pen. If the number of silver-plated pens is twice the number of gold-plated ones, what is the probability that Shelly will receive a gold-plated one?
A)
4%
B)
33%
C)
8%
D)
67%
E)
6%
Theme: Probability
Explanation:
This is a multi-step probability problem. We need to find the total number of gold-plated pens and then find the probability that one specific participant (Shelly) receives one.
1. Find the total number of prize-winning pens:
12% of the 1500 participants will receive a pen.
Total Pens = $0.12 \times 1500 = 180$ pens.
2. Find the number of gold-plated pens:
The prize pens are either silver or gold. Let $G$ be the number of gold pens and $S$ be the number of silver pens.
We know $S = 2G$ (silver-plated is twice gold-plated).
We also know $S + G = 180$ (total pens).
Substitute $S = 2G$ into the total equation:
$(2G) + G = 180$
$3G = 180$
$G = 60$ gold-plated pens.
3. Calculate the probability for Shelly:
The probability that Shelly (one specific participant) receives a gold-plated pen is the number of gold-plated pens divided by the total number of participants.
$P(\text{Gold Pen}) = \frac{\text{Number of Gold Pens}}{\text{Total Participants}}$
$P(\text{Gold Pen}) = \frac{60}{1500}$
Simplify the fraction:
$P(\text{Gold Pen}) = \frac{6}{150} = \frac{1}{25} = 0.04$
As a percentage, $0.04 \times 100 = 4\%$.
Answer:→A) 4%
7
7. Two consecutive discounts of 10% and 20% are equal to a single discount of:
A)
28%
B)
25%
C)
30%
D)
18%
E)
15%
Theme: Percentage Calculation
Explanation:
To find the total discount, we can assume a hypothetical original price, for example, 100 euros.
1. Apply the first discount (10%):
A 10% discount on 100 euros is 10 euros.
New price = $100 - 10 = 90$ euros.
Alternatively: $100 \times (1 - 0.10) = 90$ euros.
2. Apply the second discount (20%) to the new price:
The 20% discount is applied to the 90 euros, not the original 100.
$20\%$ of 90 euros = $0.20 \times 90 = 18$ euros.
Final price = $90 - 18 = 72$ euros.
3. Calculate the total discount:
The price went from 100 euros to 72 euros.
Total discount = $100 - 72 = 28$ euros.
On an original price of 100, this is a 28% discount.
Answer:→A) 28%
8
8. Stacie builds a cube using 343 blocks of wood. She decides to paint the cube green. How many of the wooden blocks will have at least one side painted green?
A)
218
B)
125
C)
245
D)
238
E)
105
Theme: Spatial Reasoning / Volume
Explanation:
The problem asks for the number of blocks on the surface of a larger cube.
1. Find the dimensions of the large cube:
The total number of blocks is 343. Since it's a cube, the number of blocks along one edge (let's call it $n$) is the cube root of the total.
$n = \sqrt[3]{343}$
Since $7 \times 7 = 49$, and $49 \times 7 = 343$, the cube is $7 \times 7 \times 7$ blocks.
2. Identify the unpainted blocks:
When the large cube is painted from the outside, only the blocks on the surface are painted. The blocks in the center, forming a smaller, inner cube, will not be painted.
This inner cube will have $7 - 2 = 5$ blocks on each edge (we subtract 1 for the outer layer on each side).
So, the inner, unpainted cube is $5 \times 5 \times 5$ blocks.
3. Calculate the number of unpainted blocks:
Volume of inner cube = $5^3 = 125$ blocks.
4. Calculate the number of painted blocks:
The number of blocks with "at least one side painted" is the total number of blocks minus the unpainted blocks.
Painted blocks = Total blocks - Unpainted blocks
Painted blocks = $343 - 125 = 218$.
Answer:→A) 218
9
9. "When he takes the train, Marco always arrives at work on time."
Which of the following statements can be deduced from the preceding proposition?
A)
Marco arrived late; therefore he did not take the train.
B)
Marco arrived late; therefore he took the train.
C)
Marco arrived on time; therefore he missed the train.
D)
Marco did not take the train; therefore he arrived late.
E)
Marco took his car; therefore he arrived on time.
Theme: Logical Deduction (Modus Tollens)
Explanation:
This is a conditional logic problem.
- Let P = "Marco takes the train."
- Let Q = "Marco arrives at work on time."
The statement is: If P, then Q (P → Q).
We need to find a valid deduction.
- A) Marco arrived late; therefore he did not take the train. This is "Not Q, therefore Not P" (¬Q → ¬P). This is the contrapositive of the original statement and is logically equivalent. If he was supposed to be on time (Q) but wasn't (¬Q), then the condition P must not have happened (¬P). This is a valid deduction.
Why other options are incorrect:
- B): "Not Q, therefore P." This is a contradiction.
- C): "Q, therefore Not P." This is the "inverse" (¬P → ¬Q) stated backward, and it's not a valid deduction. He might have arrived on time by car.
- D): "Not P, therefore Not Q." This is the "inverse fallacy". We don't know what happens if he doesn't take the train. He might still be on time (e.g., by taking a car).
- E): This introduces new information ("took his car") that cannot be deduced.
Answer:→A) Marco arrived late; therefore he did not take the train.
10
10. Which process occurs within mitochondria?
A)
Cellular respiration
B)
Glycolysis
C)
Photosynthesis
D)
The methylation of sugars
E)
The formation of microbodies
Theme: Cell Biology - Mitochondria Function
Explanation:
The mitochondria are often called the "powerhouse of the cell" because cellular respiration is their primary function. This process converts glucose and oxygen into ATP (energy), carbon dioxide, and water. The mitochondria generate most of the cell's supply of ATP through cellular respiration.
Why other options are incorrect:
- B) Glycolysis: Occurs in the cytoplasm, not within mitochondria.
- C) Photosynthesis: Occurs in chloroplasts in plant cells, not in mitochondria.
- D) The methylation of sugars: Typically occurs in the endoplasmic reticulum or Golgi apparatus.
- E) The formation of microbodies: Microbodies (like peroxisomes) form from the endoplasmic reticulum.
Example chemical equation (simplified): $\ce{C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP}$
Answer:→A) Cellular respiration
11
11. What is a hydrogen bond?
A)
It is a bond between a hydrogen atom and another strongly electronegative atom (such as oxygen or nitrogen) which is present in another molecule.
B)
It is a covalent bond between hydrogen and oxygen.
C)
It is a strong bond which allows bonding between non-polar molecules.
D)
It is the bond which occurs between hydrogen and oxygen within a water molecule.
E)
It is the bond between hydrogen and ionised atoms (such as phosphorus).
Theme: Biochemistry - Chemical Bonds
Explanation:
A hydrogen bond is an electrostatic attraction, not a true covalent bond. It forms between a hydrogen atom that is covalently bonded to a highly electronegative atom (like Oxygen, Nitrogen, or Fluorine) and another nearby electronegative atom.
- They are weak individually but strong in large numbers.
- They are crucial for the structure of water ($\ce{H_2O}$), DNA (holding the two strands together), and proteins (secondary structures like alpha-helices).
Why other options are incorrect:
- B) & D): The bond within a water molecule (between H and O) is a polar covalent bond, not a hydrogen bond. A hydrogen bond is the attraction between water molecules.
- C): It is a relatively weak bond (compared to covalent bonds), and it's characteristic of polar molecules, not non-polar ones (which experience London dispersion forces).
Answer:→A) It is a bond between a hydrogen atom and another strongly electronegative atom (such as oxygen or nitrogen) which is present in another molecule.
12
12. In eukaryotic cells, Krebs cycle reactions occur:
A)
In the mitochondrial matrix
B)
On the internal membrane of the mitochondria
C)
In the cytoplasm
D)
In the large ribosomal subunit
E)
Close to the plasma membrane
Theme: Metabolism - Cellular Respiration Location
Explanation:
- The Krebs cycle (also known as the Citric Acid Cycle) is a key stage of cellular respiration.
- In eukaryotes, this cycle takes place in the mitochondrial matrix, the fluid-filled space inside the inner mitochondrial membrane.
- It follows glycolysis (which occurs in the cytoplasm) and processes acetyl-CoA to produce NADH, $\ce{FADH_2}$, and ATP/GTP.
Why other options are incorrect:
- B): The electron transport chain and oxidative phosphorylation occur on the inner mitochondrial membrane.
- C): Glycolysis occurs in the cytoplasm.
- D): Protein synthesis (translation) occurs in ribosomes.
Answer:→A) In the mitochondrial matrix
13
13. What kind of monosaccharide is glucose?
A)
hexose
B)
pentose
C)
triose
D)
tetrose
E)
nonose
Theme: Biochemistry - Carbohydrates
Explanation:
Monosaccharides (simple sugars) are classified by the number of carbon atoms they contain:
- Triose: 3 carbons (e.g., Glyceraldehyde)
- Tetrose: 4 carbons
- Pentose: 5 carbons (e.g., Ribose, Deoxyribose)
- Hexose: 6 carbons (e.g., Glucose, Fructose, Galactose)
Glucose has the chemical formula $\ce{C_6H_{12}O_6}$, meaning it has six carbon atoms. Therefore, it is a hexose. It is the primary monosaccharide used in glycolysis to generate ATP.
Answer:→A) hexose
14
14. Which pentose sugar is present in RNA nucleotides?
A)
Ribose
B)
Glucose
C)
Fructose
D)
Glycerol
E)
Lactose
Theme: Biochemistry - Nucleic Acids
Explanation:
Nucleic acids (DNA and RNA) are made of nucleotides, which consist of a phosphate group, a nitrogenous base, and a pentose (5-carbon) sugar.
- In RNA (Ribonucleic acid), the pentose sugar is Ribose.
- In DNA (Deoxyribonucleic acid), the pentose sugar is Deoxyribose, which is ribose lacking an oxygen atom at the 2' carbon.
Answer:→A) Ribose
15
15. What are carrier proteins?
A)
They are the proteins that transfer molecules and ions across the plasma membrane
B)
They are proteins that phosphorylate enzymes in the plasma membrane.
C)
They are proteins that break down phospholipids in the plasma membrane.
D)
They are proteins that transport mRNA in the nucleus.
E)
They are proteins that transport tRNA in the nucleolus.
Theme: Cell Biology - Membrane Transport
Explanation:
Carrier proteins are integral membrane proteins that facilitate the movement of specific molecules and ions across the plasma membrane. They bind to the substance, change their shape, and release it on the other side of the membrane. They are essential for transporting substances like glucose and amino acids that cannot pass through the lipid bilayer on their own.
           
                💡               
                   
There are three main types of membrane transport proteins:
1.  Channels: Create pores for specific ions/molecules. Facilitate passive transport (no ATP, down gradient).
2.  Carriers (Transporters): Bind to molecules and change shape. Can be passive (facilitated diffusion) or active.
3.  Pumps: A type of carrier that uses ATP for active transport (against gradient). Example: $\ce{Na^+/K^+}$ ATPase.
               
           
       
Answer:→A) They are the proteins that transfer molecules and ions across the plasma membrane
16
16. What is the cell's energy currency?
A)
ATP
B)
FADH2
C)
NADH
D)
Creatine
E)
NADPH
Theme: Metabolism - Bioenergetics
Explanation:
ATP (Adenosine Triphosphate) is known as the cell's primary energy currency.
Energy is stored in the high-energy phosphoanhydride bonds linking the three phosphate groups. When the terminal phosphate bond is broken (hydrolyzed) to form ADP + Pi, a significant amount of energy is released, which the cell can use to power endergonic reactions, muscle contraction, and active transport.
While NADH and $\ce{FADH_2}$ are high-energy electron carriers, they are not the direct "currency" used for most cellular work; their energy is primarily used to generate ATP during oxidative phosphorylation.
Answer:→A) ATP
17
17. Which kind of reaction is ATP hydrolysis?
A)
exergonic
B)
endergonic
C)
condensation
D)
Oxidation-reduction
E)
Lipolysis
Theme: Thermodynamics in Biology
Explanation:
ATP hydrolysis is the reaction $\ce{ATP + H_2O -> ADP + P_i}$ (inorganic phosphate).
- This reaction breaks a high-energy phosphoanhydride bond and releases energy.
- Reactions that release free energy (have a negative Gibbs free energy change, $\Delta G < 0$) are called exergonic.
- The cell couples this exergonic reaction to power endergonic reactions (which require energy).
Why other options are incorrect:
- B) Endergonic: These reactions consume energy ($Delta G > 0$). The synthesis of ATP from ADP is endergonic.
- C) Condensation: These reactions join molecules by removing water. Hydrolysis is the opposite.
- D) Oxidation-reduction (Redox): These involve the transfer of electrons. While redox reactions generate the energy to make ATP, the hydrolysis of ATP itself is not a redox reaction.
- E) Lipolysis: This is the breakdown of lipids (fats).
Answer:→A) exergonic
18
18. The presence of intercellular compartmentalisation is a characteristic of which organisms?
A)
Of eukaryotes
B)
Of viruses
C)
Of bacteria
D)
Of prokaryotes
E)
Only of algae
Theme: Cell Biology - Eukaryotes vs Prokaryotes
Explanation:
Intercellular compartmentalization refers to the presence of membrane-bound organelles (like the nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, etc.) within the cell.
- This complex internal organization is the defining characteristic of eukaryotic cells. It allows different metabolic processes to occur simultaneously in specialized compartments, increasing efficiency.
Why other options are incorrect:
- C) & D) Bacteria and prokaryotes lack membrane-bound organelles. Their genetic material and metabolic processes occur in the cytoplasm.
- B) Viruses are not cells; they are infectious particles that require a host cell to replicate.
- E) Algae are eukaryotes, but compartmentalization is not unique to them; it's found in all eukaryotes (plants, animals, fungi, protists).
Answer:→A) Of eukaryotes
19
19. Which intracellular structure is composed of microtubules?
A)
The centriole
B)
The nucleus
C)
The Golgi apparatus
D)
The nucleolus
E)
The endoplasmic reticulum
Theme: Cell Biology - Cytoskeleton
Explanation:
Microtubules are one of the three main components of the cytoskeleton.
- Centrioles are cylindrical structures made of nine triplets of microtubules, arranged in a "9+0" pattern. They are crucial for forming the centrosome (Microtubule Organizing Center) and the basal bodies of cilia and flagella.
Why other options are incorrect:
- B), C), E): The nucleus, Golgi apparatus, and endoplasmic reticulum are all membrane-bound organelles, not composed of microtubules (though microtubules act as "tracks" to move them).
- D) The nucleolus: A dense structure within the nucleus responsible for ribosome synthesis.
           
                💡               
                   
Three main types of cytoskeletal filaments:
1.  Actin Filaments (Microfilaments) (7nm): Involved in cell shape, muscle contraction, and cytokinesis.
2.  Intermediate Filaments (10nm): Provide mechanical strength and support (e.g., keratin, lamins).
3.  Microtubules (25nm): Hollow tubes of tubulin. Act as intracellular "highways," form the mitotic spindle, and are the core of cilia, flagella, and centrioles.
               
           
       
Answer:→A) The centriole
20
20. Mitochondria have:
A)
An outer membrane and a very selective inner membrane
B)
Only a very selective outer membrane
C)
An outer membrane, an intermediate membrane, and a very selective inner membrane
D)
An outer membrane consisting of a phospholipid monolayer
E)
A very selective membrane in which no proteins are present
Theme: Cell Biology - Mitochondrial Structure
Explanation:
Mitochondria are double-membraned organelles.
- The outer membrane is relatively permeable to small molecules due to porin proteins.
- The inner membrane is highly folded (into cristae) and is very selective. It strictly controls what passes into the matrix and contains the proteins of the electron transport chain and ATP synthase. This selectivity is essential for maintaining the proton gradient that drives ATP synthesis.
Why other options are incorrect:
- B): Mitochondria have two membranes, not one.
- C): There is no "intermediate membrane," only an outer membrane, an inner membrane, and an intermembrane space.
- D): All biological membranes, including the outer mitochondrial membrane, are phospholipid bilayers, not monolayers.
- E): The inner membrane is highly selective precisely because it is packed with transport proteins, as well as the proteins for the ETC.
Answer:→A) An outer membrane and a very selective inner membrane
21
21. What is an anticodon?
A)
The sequence of three nucleotides found on the tRNA corresponding to a codon on the mRNA.
B)
A sequence three nucleotides transcribed from the mRNA and translated by rRNA
C)
A part of the DNA that codes for a specific amino acid
D)
A terminal triplet of rRNA that binds a specific amino acid
E)
The sequence of three mRNA nucleotides corresponding to a DNA codon
Theme: Molecular Biology - Translation
Explanation:
During translation (protein synthesis), a codon (a three-nucleotide sequence on mRNA) specifies a particular amino acid.
- A transfer RNA (tRNA) molecule carries the corresponding amino acid to the ribosome.
- The tRNA molecule has a complementary three-nucleotide sequence called the anticodon, which base-pairs with the mRNA codon, ensuring the correct amino acid is added to the growing polypeptide chain.
Why other options are incorrect:
- C): A three-nucleotide sequence on DNA is just a "triplet" or part of a gene.
- E): A three-nucleotide sequence on mRNA is a codon, not an anticodon.
Answer:→A) The sequence of three nucleotides found on the tRNA corresponding to a codon on the mRNA.
22
22. What are ribosomes made of?
A)
RNA and proteins
B)
DNA and proteins
C)
DNA and lipids
D)
RNA and DNA
E)
RNA, DNA, and proteins
Theme: Cell Biology - Ribosomes
Explanation:
Ribosomes are the molecular machines responsible for protein synthesis (translation).
- They are complex structures composed of ribosomal RNA (rRNA) and proteins.
- The rRNA forms the structural core of the ribosome and catalyzes the peptide bond formation, making it a "ribozyme". The proteins stabilize the structure and assist in the process.
- Ribosomes consist of two subunits (large and small) that assemble on the mRNA to begin translation.
Answer:→A) RNA and proteins
23
23. The cell membrane consists of:
A)
a double phospholipid layer with hydrophobic tails facing inward and the presence of integral and peripheral proteins
B)
Cholesterol and phospholipid molecules enclosing a protein layer
C)
A double layer of triglycerides and cholesterol
D)
A glycoprotein layer containing phospholipids and cholesterol
E)
A layer of fatty acids and globular proteins containing phospholipids and cholesterol
Theme: Cell Biology - Plasma Membrane Structure
Explanation:
The fluid mosaic model describes the cell membrane. Its fundamental structure is a phospholipid bilayer.
- In this bilayer, the hydrophilic (water-loving) phosphate heads face the watery environment inside and outside the cell.
- The hydrophobic (water-repelling) fatty acid tails face inward, creating a nonpolar barrier.
- Proteins (integral and peripheral) are embedded within or attached to this bilayer, carrying out functions like transport and signaling. Cholesterol is also present, affecting fluidity.
Answer:→A) a double phospholipid layer with hydrophobic tails facing inward and the presence of integral and peripheral proteins
24
24. In protein synthesis, what is translation?
A)
It is the process by which mRNA is read and converted into a specific sequence of amino acids.
B)
It is the process of transcribing the mRNA sequence into a corresponding DNA molecule.
C)
It is the process of specific recognition of rRNA by amino acids.
D)
It is the process in which DNA is read and the corresponding mRNA produced.
E)
It is the process of pairing between DNA codons and tRNA anticodons.
Theme: Molecular Biology - Central Dogma
Explanation:
Translation is the second major step of gene expression (part of the "Central Dogma": DNA → RNA → Protein).
- It is the process where the genetic information encoded in a messenger RNA (mRNA) molecule is used to synthesize a specific protein.
- Ribosomes "read" the mRNA sequence in three-nucleotide units called codons. Each codon specifies a particular amino acid, which is brought by a tRNA. The ribosome links these amino acids together to form a polypeptide chain.
Why other options are incorrect:
- B): This is reverse transcription (occurs in retroviruses).
- D): This is transcription (DNA → RNA).
- E): Pairing occurs between mRNA codons and tRNA anticodons.
Answer:→A) It is the process by which mRNA is read and converted into a specific sequence of amino acids.
25
25. What are the principal components of the cytoskeleton?
A)
Microtubules, microfilaments, and intermediate filaments
B)
Microtubules, myosin, and filamin
C)
Microtubules, dynein, and myosin
D)
Actin, myosin and dynein
E)
Collagen fibres and reticular fibres
Theme: Cell Biology - Cytoskeleton
Explanation:
The cytoskeleton provides structural support to the cell, facilitates movement, and organizes intracellular components. It is primarily composed of three types of protein filaments:
1.  Microfilaments (Actin filaments): Thin, flexible fibers involved in cell shape, muscle contraction, and cell crawling.
2.  Intermediate filaments: Rope-like fibers that provide mechanical strength and resist stress (e.g., keratin).
3.  Microtubules: Hollow tubes made of tubulin, involved in intracellular transport, forming the mitotic spindle, and making up cilia and flagella.
This corresponds to option A.
Why other options are incorrect:
- B, C, D): Myosin and dynein are motor proteins that "walk" along microtubules or microfilaments; they are not the primary structural components themselves (though actin is part of microfilaments).
- E): Collagen and reticular fibers are components of the extracellular matrix (outside the cell), not the cytoskeleton (inside the cell).
Answer:→A) Microtubules, microfilaments, and intermediate filaments
26
26. The term "allele" defines:
A)
one of several alternative forms of a gene
B)
A coding DNA base for a specific amino acid
C)
A hereditary trait only found in haploid cells
D)
The phenotypic manifestation of a given gene
E)
A set of coding DNA triplets for a specific amino acid
Theme: Genetics
Explanation:
An allele is one of two or more versions of a gene found at the same place (locus) on a chromosome. For example, the gene for flower color in pea plants has a dominant allele (P) for purple flowers and a recessive allele (p) for white flowers. An individual inherits one allele from each parent.
Why other options are incorrect:
- B) & E): A three-base sequence that codes for an amino acid is a codon.
- D): The phenotypic manifestation (observable trait, like "purple flowers") is the phenotype, not the allele itself.
Answer:→A) one of several alternative forms of a gene
27
27. In a heterozygous condition, an allele can certainly express itself when:
A)
dominant
B)
recessive
C)
mutated
D)
multiple
E)
associated
Theme: Genetics - Mendelian Inheritance
Explanation:
A heterozygous condition means an individual has two different alleles for a specific gene (e.g., $Aa$).
- A dominant allele ($A$) is one that expresses its trait (phenotype) even when only one copy is present.
- A recessive allele ($a$) only expresses its trait when two copies are present (homozygous recessive, $aa$).
Therefore, in a heterozygous individual ($Aa$), the dominant allele ($A$) is the one that will "certainly express itself."
Answer:→A) dominant
28
28. What are mutations?
A)
Alterations in the genetic information of a cell
B)
Alteration in the energy metabolism of a cell
C)
Alterations in enzyme functionality during zygote formation
D)
Alterations in the active transport system of biological membranes
E)
Alterations in the mechanism of cell division.
Theme: Genetics - Mutations
Explanation:
A mutation is a change or alteration in the genetic information (the DNA sequence) of a cell. This can range from a single base-pair change (point mutation) to large-scale changes like deletions, insertions, or rearrangements of chromosomes. Mutations are the ultimate source of genetic variation.
Why other options are incorrect:
- B, C, D, E): These are all potential consequences or results of a mutation, but they are not the definition of the mutation itself. A mutation in a gene might cause an alteration in energy metabolism, enzyme function, active transport, or cell division, but the mutation is the change in the DNA.
Answer:→A) Alterations in the genetic information of a cell
29
29. Translation is a process which:
A)
leads to the synthesis of polypeptide chains from mRNA
B)
occurs in the nucleus of eukaryotic cells
C)
leads to the synthesis of RNA from DNA
D)
is very similar to transcription
E)
Is exclusively eukaryotic
Theme: Molecular Biology - Translation
Explanation:
Translation is the process where ribosomes synthesize polypeptide chains (proteins) using the information encoded in an mRNA molecule.
Why other options are incorrect:
- B): In eukaryotes, translation occurs in the cytoplasm (on free ribosomes) or on the rough endoplasmic reticulum. Transcription occurs in the nucleus.
- C): The synthesis of RNA from DNA is transcription.
- D): Translation (RNA to protein) and transcription (DNA to RNA) are fundamentally different processes.
- E): Translation is a universal process, occurring in both prokaryotes and eukaryotes.
Answer:→A) leads to the synthesis of polypeptide chains from mRNA
30
30. If the sequence CCGTTATTGA is found on a strand of DNA helix, what sequence will be found on the complementary strand?
A)
GGCAATAACT
B)
AGTTATTGCC
C)
GGACATCCCT
D)
CGCACCTCCT
E)
GGCAATTAAT
Theme: Molecular Biology - DNA Structure
Explanation:
DNA is a double helix with complementary base pairing rules:
- Adenine (A) pairs with Thymine (T).
- Guanine (G) pairs with Cytosine (C).
We need to find the complementary sequence to the template strand CCGTTATTGA:
- C → G
- C → G
- G → C
- T → A
- T → A
- A → T
- T → A
- T → A
- G → C
- A → T
The complementary strand is GGCAATAACT.
Answer:→A) GGCAATAACT
31
31. Replication is the process through which:
A)
DNA is used as a template to synthesize new DNA molecules
B)
DNA is used as a template to synthesize RNA molecules
C)
RNA is used as a template to synthesize protein molecules
D)
RNA is used as a template to synthesize new RNA molecules
E)
Proteins are used as a template to synthesize DNA molecules
Theme: Molecular Biology - Central Dogma
Explanation:
Replication is the biological process by which a double-stranded DNA molecule is copied to produce two identical DNA molecules. It occurs during the S phase of the cell cycle to ensure that each daughter cell receives a complete set of genetic information.
Why other options are incorrect:
- B) DNA is used as a template to synthesize RNA molecules: This process is called transcription.
- C) RNA is used as a template to synthesize protein molecules: This process is called translation.
- D) RNA is used as a template to synthesize new RNA molecules: This is RNA replication, which occurs in some viruses but is not the standard definition of replication in cells.
- E) Proteins are used as a template to synthesize DNA molecules: This process (reverse translation) does not occur in biology. Reverse transcription (RNA to DNA) occurs, but not protein to DNA.
Answer:→A) DNA is used as a template to synthesize new DNA molecules
32
32. The prokaryotic operon is:
A)
A functional unit composed of a group of adjacent genes, co-ordinately controlled, and of DNA sequences with regulatory functions.
B)
A group of adjacent genes that are transcribed independently of each other.
C)
A protein complex that catalyzes the process of protein synthesis.
D)
An RNA complex that is involved in the replication of DNA.
E)
A DNA sequence element that only codes for a single protein without any regulatory function.
Theme: Gene Regulation - Prokaryotic Operon
Explanation:
An operon is a fundamental genetic regulatory system in prokaryotes. It consists of a cluster of genes (structural genes) that are transcribed together as a single mRNA unit, controlled by the same promoter and regulatory DNA sequences (like an operator). This allows for the coordinated control (co-regulation) of genes involved in a common metabolic pathway.
Why other options are incorrect:
- B) A group of adjacent genes that are transcribed independently: This is the opposite of an operon, where genes are co-ordinately controlled and transcribed together.
- C) A protein complex that catalyzes... protein synthesis: This describes a ribosome.
- D) An RNA complex that is involved in... replication: This might describe parts of the replication machinery (like primase which makes an RNA primer), but it is not an operon.
- E) A DNA sequence... without any regulatory function: This is incorrect because operons are defined by their regulatory functions (promoter, operator) that control the structural genes.
Answer:→A) A functional unit composed of a group of adjacent genes, co-ordinately controlled, and of DNA sequences with regulatory functions.
33
33. A mixture of $0.3 \text{ mol of } \ce{N_2}$, $0.5 \text{ mol of } \ce{CO_2}$, and $0.4 \text{ mol of } \ce{O_2}$ exerts a total pressure of $2.4 \text{ atm}$ on the walls of the vessel that contains it. What is the partial pressure exerted by the nitrogen ($\ce{N_2}$)?
A)
$0.6 \text{ atm}$
B)
$1.0 \text{ atm}$
C)
$0.8 \text{ atm}$
D)
$2.4 \text{ atm}$
E)
$0.3 \text{ atm}$
Theme: Gas Laws - Dalton's Law of Partial Pressures
Explanation:
According to Dalton's Law, the partial pressure of a gas in a mixture is equal to its mole fraction multiplied by the total pressure.
1. Find total moles:
$n_{\text{total}} = n_{\ce{N_2}} + n_{\ce{CO_2}} + n_{\ce{O_2}} = 0.3 + 0.5 + 0.4 = 1.2 \text{ mol}$
2. Find mole fraction of $\ce{N_2}$:
$X_{\ce{N_2}} = \frac{n_{\ce{N_2}}}{n_{\text{total}}} = \frac{0.3 \text{ mol}}{1.2 \text{ mol}} = 0.25$
3. Calculate partial pressure of $\ce{N_2}$:
$P_{\ce{N_2}} = X_{\ce{N_2}} \times P_{\text{total}} = 0.25 \times 2.4 \text{ atm} = 0.6 \text{ atm}$
Why other options are incorrect:
- B) $1.0 \text{ atm}$: This would be the partial pressure of $\ce{CO_2}$ ($(\frac{0.5}{1.2}) \times 2.4 \text{ atm}$).
- C) $0.8 \text{ atm}$: This would be the partial pressure of $\ce{O_2}$ ($(\frac{0.4}{1.2}) \times 2.4 \text{ atm}$).
- D) $2.4 \text{ atm}$: This is the total pressure of the mixture, not the partial pressure of nitrogen.
- E) $0.3 \text{ atm}$: This is the number of moles of nitrogen, not its partial pressure.
Answer:→A) $0.6 \text{ atm}$
34
34. A gas, confined in a rigid cylinder and maintained at a temperature of $-3 \text{ °C}$ exerts a pressure of $9 \text{ atm}$. What pressure would the same gas exert if it were heated to $27 \text{ °C}$?
A)
$10 \text{ atm}$
B)
$8.1 \text{ atm}$
C)
$9 \text{ atm}$
D)
$-81 \text{ atm}$
E)
$1 \text{ atm}$
Theme: Gas Laws - Gay-Lussac's Law
Explanation:
Since the gas is in a rigid cylinder, its volume is constant. Gay-Lussac's Law states that for a fixed mass of gas at constant volume, the pressure is directly proportional to the absolute temperature (in Kelvin).
$\frac{P_1}{T_1} = \frac{P_2}{T_2}$
1. Convert temperatures to Kelvin:
$T_1 = -3 \text{ °C} + 273.15 \approx 270 \text{ K}$
$T_2 = 27 \text{ °C} + 273.15 \approx 300 \text{ K}$
2. Set up the equation:
$P_1 = 9 \text{ atm}$
$\frac{9 \text{ atm}}{270 \text{ K}} = \frac{P_2}{300 \text{ K}}$
3. Solve for $P_2$:
$P_2 = (9 \text{ atm}) \times (\frac{300 \text{ K}}{270 \text{ K}}) = 9 \times (\frac{10}{9}) = 10 \text{ atm}$
Why other options are incorrect:
- B) $8.1 \text{ atm}$: This results from an incorrect ratio, possibly $\frac{27}{30} \times 9$.
- C) $9 \text{ atm}$: The pressure would only remain the same if the temperature did not change.
- D) $-81 \text{ atm}$: This results from incorrectly using Celsius in the ratio ($\frac{27}{-3} \times 9$), which is invalid. Absolute temperature must be used.
- E) $1 \text{ atm}$: This would be $\frac{30}{270} \times 9$, an incorrect calculation.
Answer:→A) $10 \text{ atm}$
35
35. Which of the following compounds forms a hydroxide when reacting with water?
A)
$\ce{BaO}$
B)
$\ce{CO_2}$
C)
$\ce{SO_3}$
D)
$\ce{SiO_2}$
E)
$\ce{N_2O_5}$
Theme: Acids and Bases - Oxides
Explanation:
Basic oxides (metal oxides) react with water to form bases (hydroxides). Acidic oxides (non-metal oxides) react with water to form acids.
Barium oxide ($\ce{BaO}$) is an oxide of an alkaline earth metal, making it a basic oxide. It reacts with water to form barium hydroxide:
$\ce{BaO + H_2O -> Ba(OH)_2}$
Why other options are incorrect:
- B) $\ce{CO_2}$: Carbon dioxide is an acidic oxide. It reacts with water to form carbonic acid ($\ce{H_2CO_3}$).
- C) $\ce{SO_3}$: Sulfur trioxide is an acidic oxide. It reacts with water to form sulfuric acid ($\ce{H_2SO_4}$).
- D) $\ce{SiO_2}$: Silicon dioxide (sand) is generally considered unreactive with water under normal conditions.
- E) $\ce{N_2O_5}$: Dinitrogen pentoxide is an acidic oxide. It reacts with water to form nitric acid ($\ce{HNO_3}$).
Answer:→A) $\ce{BaO}$
36
36. Given the reaction $\ce{4 FeS_2 + 11 O_2 -> 2 Fe_2O_3 + 8 SO_2}$, which of the following statements is correct based on the stoichiometry?
A)
From $2 \text{ mol of } \ce{FeS_2}$ and $11 \text{ mol of } \ce{O_2}$, $1 \text{ mol of } \ce{Fe_2O_3}$ can be obtained.
B)
From $4 \text{ mol of } \ce{FeS_2}$ and $11 \text{ mol of } \ce{O_2}$, $4 \text{ mol of } \ce{Fe_2O_3}$ can be obtained.
C)
From $4 \text{ mol of } \ce{FeS_2}$ and $11 \text{ mol of } \ce{O_2}$, $8 \text{ mol of } \ce{Fe_2O_3}$ can be obtained.
D)
From $2 \text{ mol of } \ce{FeS_2}$ and $5.5 \text{ mol of } \ce{O_2}$, $2 \text{ mol of } \ce{Fe_2O_3}$ can be obtained.
E)
From $4 \text{ mol of } \ce{FeS_2}$, $11 \text{ mol of } \ce{O_2}$ is not needed.
Theme: Stoichiometry - Limiting Reactants
Explanation:
The balanced equation is: $\ce{4 FeS_2 + 11 O_2 -> 2 Fe_2O_3 + 8 SO_2}$
This tells us the molar ratio: $4 \text{ mol } \ce{FeS_2} : 11 \text{ mol } \ce{O_2} : 2 \text{ mol } \ce{Fe_2O_3}$
Let's analyze statement A: We have $2 \text{ mol of } \ce{FeS_2}$ and $11 \text{ mol of } \ce{O_2}$.
1. Find the limiting reactant:
* Based on $\ce{FeS_2}$: $2 \text{ mol } \ce{FeS_2} \times (\frac{11 \text{ mol } \ce{O_2}}{4 \text{ mol } \ce{FeS_2}}) = 5.5 \text{ mol } \ce{O_2}$ needed. We have $11 \text{ mol } \ce{O_2}$, so $\ce{O_2}$ is in excess and $\ce{FeS_2}$ is the limiting reactant.
2. Calculate product based on limiting reactant:
* $2 \text{ mol } \ce{FeS_2} \times (\frac{2 \text{ mol } \ce{Fe_2O_3}}{4 \text{ mol } \ce{FeS_2}}) = 1 \text{ mol } \ce{Fe_2O_3}$
Statement A is correct.
Why other options are incorrect:
- B) & C): The equation clearly shows that $4 \text{ mol } \ce{FeS_2}$ produces $2 \text{ mol } \ce{Fe_2O_3}$, not 4 or 8.
- D): $2 \text{ mol } \ce{FeS_2}$ is the limiting reactant and, as calculated, produces $1 \text{ mol } \ce{Fe_2O_3}$, not 2.
- E): According to the balanced equation, $4 \text{ mol } \ce{FeS_2}$ requires exactly $11 \text{ mol } \ce{O_2}$ to react completely.
Answer:→A) From $2 \text{ mol of } \ce{FeS_2}$ and $11 \text{ mol of } \ce{O_2}$, $1 \text{ mol of } \ce{Fe_2O_3}$ can be obtained.
37
37. How many mL of water must be added to $15 \text{ mL}$ of a $0.25 \text{ M}$ solution of $\ce{H_2SO_4}$ to obtain a $0.05 \text{ M}$ solution?
A)
$60 \text{ mL}$
B)
$75 \text{ mL}$
C)
$15 \text{ mL}$
D)
$50 \text{ mL}$
E)
$3.75 \text{ mL}$
Theme: Solutions - Dilution
Explanation:
This is a dilution problem, which can be solved using the formula $M_1V_1 = M_2V_2$, where M is molarity and V is volume.
* $M_1 = 0.25 \text{ M}$ (initial concentration)
* $V_1 = 15 \text{ mL}$ (initial volume)
* $M_2 = 0.05 \text{ M}$ (final concentration)
* $V_2 = ?$ (final volume)
1. Solve for the final volume ($V_2$):
$(0.25 \text{ M}) \times (15 \text{ mL}) = (0.05 \text{ M}) \times V_2$
$3.75 = 0.05 \times V_2$
$V_2 = \frac{3.75}{0.05} = 75 \text{ mL}$
2. Find the volume of water to add:
The final volume is $75 \text{ mL}$. Since we started with $15 \text{ mL}$, the amount of water to add is the difference.
$V_{\text{add}} = V_2 - V_1 = 75 \text{ mL} - 15 \text{ mL} = 60 \text{ mL}$
Why other options are incorrect:
- B) $75 \text{ mL}$: This is the total final volume of the solution, not the volume of water added.
- C) $15 \text{ mL}$: This is the initial volume.
- D) $50 \text{ mL}$: This would result from an incorrect calculation.
- E) $3.75 \text{ mL}$: This is the result of $M_1 \times V_1$, which is the number of millimoles.
Answer:→A) $60 \text{ mL}$
38
38. How many moles of $\ce{Na^+}$ ions are present in $250 \text{ mL}$ of a $1.2 \text{ M}$ solution of $\ce{Na_2SO_4}$?
A)
$0.6 \text{ mol}$
B)
$0.3 \text{ mol}$
C)
$1.2 \text{ mol}$
D)
$0.48 \text{ mol}$
E)
$300 \text{ mol}$
Theme: Solutions - Molarity and Stoichiometry
Explanation:
1. Calculate moles of $\ce{Na_2SO_4}$:
* Convert volume to Liters: $V = 250 \text{ mL} = 0.250 \text{ L}$
* $\text{Moles} = \text{Molarity} \times \text{Volume (L)}$
* $\text{Moles of } \ce{Na_2SO_4} = 1.2 \text{ mol/L} \times 0.250 \text{ L} = 0.3 \text{ mol}$
2. Find moles of $\ce{Na^+}$ ions:
When sodium sulfate ($\ce{Na_2SO_4}$) dissolves, it dissociates: $\ce{Na_2SO_4(s) -> 2Na^+(aq) + SO_4^{2-}(aq)}$
For every 1 mole of $\ce{Na_2SO_4}$, 2 moles of $\ce{Na^+}$ ions are produced.
* $\text{Moles of } \ce{Na^+} = (\text{Moles of } \ce{Na_2SO_4}) \times 2$
* $\text{Moles of } \ce{Na^+} = 0.3 \text{ mol} \times 2 = 0.6 \text{ mol}$
Why other options are incorrect:
- B) $0.3 \text{ mol}$: This is the number of moles of the compound $\ce{Na_2SO_4}$, not the moles of $\ce{Na^+}$ ions.
- C) $1.2 \text{ mol}$: This is the molarity of the solution, not the number of moles.
- D) $0.48 \text{ mol}$: This might result from an incorrect calculation, perhaps $1.2 / 2.5$.
- E) $300 \text{ mol}$: This is the result of $1.2 \times 250$, which incorrectly mixes units (Molarity and mL).
Answer:→A) $0.6 \text{ mol}$
39
39. In the reaction $\ce{NH_3 + BF_3 <=> NH_3BF_3}$, how is ammonia ($\ce{NH_3}$) acting?
A)
As a Lewis base
B)
As a Lewis acid
C)
As a Brønsted-Lowry acid
D)
As an Arrhenius acid
E)
As both a Lewis acid and a Brønsted-Lowry base
Theme: Acid-Base Theories - Lewis Acids and Bases
Explanation:
Let's analyze the reaction using the Lewis definition:
Lewis Base:* An electron pair donor.
Lewis Acid:* An electron pair acceptor.
In ammonia ($\ce{NH_3}$), the nitrogen atom has a lone pair of electrons. Boron trifluoride ($\ce{BF_3}$) is electron-deficient because the boron atom has an incomplete octet.
The $\ce{NH_3}$ molecule donates its lone pair of electrons to the $\ce{BF_3}$ molecule to form a coordinate covalent bond. Therefore, $\ce{NH_3}$ is acting as a Lewis base.
Why other options are incorrect:
- B) As a Lewis acid: $\ce{NH_3}$ is donating electrons, not accepting them. $\ce{BF_3}$ is the Lewis acid.
- C) As a Brønsted-Lowry acid: This theory involves proton ($\ce{H^+}$) donation. $\ce{NH_3}$ is not donating a proton in this reaction.
- D) As an Arrhenius acid: This theory requires the substance to produce $\ce{H^+}$ in water, which is not what is happening here.
- E) As both a Lewis acid and a Brønsted-Lowry base: It is acting as a Lewis base, not a Lewis acid.
Answer:→A) As a Lewis base
40
40. In the reaction $\ce{Zn(s) + 4HNO_3(aq) -> Zn(NO_3)_2(aq) + 2NO_2(g) + 2H_2O(l)}$, which species acts as the reducing agent?
A)
$\ce{Zn(s)}$
B)
$\ce{HNO_3(aq)}$
C)
$\ce{NO_2(g)}$
D)
$\ce{Zn(NO_3)_2(aq)}$
E)
$\ce{H_2O(l)}$
Theme: Redox Reactions - Oxidizing and Reducing Agents
Explanation:
A reducing agent is a substance that gets oxidized* (loses electrons) and causes another substance to be reduced.
An oxidizing agent is a substance that gets reduced* (gains electrons) and causes another substance to be oxidized.
Let's assign oxidation states:
* $\ce{Zn(s)}$: Oxidation state = $0$
* $\ce{HNO_3}$: H is +1, O is -2. So, $1 + N + 3(-2) = 0 \Rightarrow N = +5$
* $\ce{Zn(NO_3)_2}$: $\ce{NO_3}$ is a -1 ion. So, $Zn + 2(-1) = 0 \Rightarrow Zn = +2$
* $\ce{NO_2}$: O is -2. So, $N + 2(-2) = 0 \Rightarrow N = +4$
Analysis:
Zinc ($\ce{Zn}$) goes from an oxidation state of $0$ to $+2$. It has lost electrons, so it is oxidized. Therefore, $\ce{Zn(s)}$ is the reducing agent*.
Nitrogen (in $\ce{HNO_3}$) goes from $+5$ to $+4$ (in $\ce{NO_2}$). It has gained electrons, so it is reduced. Therefore, $\ce{HNO_3}$ is the oxidizing agent*.
Why other options are incorrect:
- B) $\ce{HNO_3(aq)}$: This is the oxidizing agent, as it gets reduced.
- C) $\ce{NO_2(g)}$: This is a product of the reduction.
- D) $\ce{Zn(NO_3)_2(aq)}$: This is a product of the oxidation.
- E) $\ce{H_2O(l)}$: This is a product and its atoms do not change oxidation state.
Answer:→A) $\ce{Zn(s)}$
41
41. Which of the following compounds has the most hydrogen atoms?
A)
2,3-Dimethylpentane
B)
Cyclohexane
C)
1,2-Dimethylcyclobutane
D)
2,3-Dimethyl-2-butene
E)
2-Hexanol
Theme: Organic Chemistry - Nomenclature and Molecular Formulas
Explanation:
Let's determine the molecular formula for each compound to count the hydrogen atoms.
A) 2,3-Dimethylpentane: Pentane ($\ce{C_5}$) + 2 Methyl groups ($2 \times \ce{C_1}$) = $\ce{C_7}$. It's a saturated alkane, so its formula is $\ce{C_nH_{2n+2}}$. $\ce{C_7H_{(2 \times 7)+2}} = \ce{C_7H_{16}}$. (16 H)*
B) Cyclohexane: It's a cycloalkane with 6 carbons. The general formula is $\ce{C_nH_{2n}}$. $\ce{C_6H_{12}}$. (12 H)*
C) 1,2-Dimethylcyclobutane: Cyclobutane ($\ce{C_4}$) + 2 Methyl groups ($2 \times \ce{C_1}$) = $\ce{C_6}$. As a cycloalkane, its base formula is $\ce{C_6H_{12}}$. (12 H)*
D) 2,3-Dimethyl-2-butene: Butene ($\ce{C_4}$) + 2 Methyl groups ($2 \times \ce{C_1}$) = $\ce{C_6}$. It has one double bond (alkene), so its formula is $\ce{C_nH_{2n}}$. $\ce{C_6H_{12}}$. (12 H)*
E) 2-Hexanol: This is an alcohol derived from hexane ($\ce{C_6H_{14}}$) by replacing one H with an OH group. The formula is $\ce{C_6H_{13}OH}$. It has $13 + 1 = 14$ hydrogen atoms. (14 H)*
Comparing the counts: 16, 12, 12, 12, 14. The highest number is 16.
Answer:→A) 2,3-Dimethylpentane
42
42. Which of the following molecules does NOT contain a carbon-oxygen double bond ($\ce{C=O}$)?
A)
Dimethyl ether
B)
Acetaldehyde
C)
Acetone
D)
Acetic acid
E)
Methyl acetate
Theme: Organic Chemistry - Functional Groups
Explanation:
A carbon-oxygen double bond ($\ce{C=O}$) is characteristic of the carbonyl group, which is found in aldehydes, ketones, carboxylic acids, and esters.
A) Dimethyl ether ($\ce{CH_3-O-CH_3}$): This is an ether. It contains two carbon-oxygen single* bonds, but no double bonds.
B) Acetaldehyde ($\ce{CH_3CHO}$): This is an aldehyde*. It contains a $\ce{C=O}$ bond.
C) Acetone ($\ce{CH_3COCH_3}$): This is a ketone*. It contains a $\ce{C=O}$ bond.
D) Acetic acid ($\ce{CH_3COOH}$): This is a carboxylic acid*. It contains a $\ce{C=O}$ bond.
E) Methyl acetate ($\ce{CH_3COOCH_3}$): This is an ester*. It contains a $\ce{C=O}$ bond.
Therefore, dimethyl ether is the only compound in the list that lacks a $\ce{C=O}$ double bond.
Answer:→A) Dimethyl ether
43
43. One atmosphere ($1 \text{ atm}$) of pressure is equivalent to all of the following EXCEPT:
A)
$1013.25 \text{ kPa}$
B)
$101325 \text{ Pa}$
C)
$1013.25 \text{ mbar}$
D)
$760 \text{ mmHg}$
E)
$760 \text{ torr}$
Theme: Units - Pressure Conversions
Explanation:
Standard atmospheric pressure ($1 \text{ atm}$) is defined by several equivalent values. Let's check the options.
* $1 \text{ atm} = 101325 \text{ Pa}$. (This is a standard definition). Option B is correct.
Since $1 \text{ kPa} = 1000 \text{ Pa}$, $101325 \text{ Pa} = 101.325 \text{ kPa}$. Option A states $1013.25 \text{ kPa}$, which is $10$ times larger. Thus, Option A is not equivalent.*
* $1 \text{ bar} = 100,000 \text{ Pa}$, so $1 \text{ mbar} = 100 \text{ Pa}$. $101325 \text{ Pa} / 100 \text{ Pa/mbar} = 1013.25 \text{ mbar}$. Option C is correct.
* $1 \text{ atm} = 760 \text{ mmHg}$ (by definition, based on the height of a mercury column). Option D is correct.
* $1 \text{ torr}$ is defined as $1 \text{ mmHg}$. Therefore, $1 \text{ atm} = 760 \text{ torr}$. Option E is correct.
Why other options are correct:
- B) $101325 \text{ Pa}$: This is the standard SI unit definition.
- C) $1013.25 \text{ mbar}$: This is a common unit in meteorology and is equivalent.
- D) $760 \text{ mmHg}$: This is the manometric definition.
- E) $760 \text{ torr}$: This is equivalent to mmHg by definition.
Answer:→A) $1013.25 \text{ kPa}$
44
44. How many nitrogen atoms are contained in $0.7 \text{ g}$ of nitrogen gas ($\ce{N_2}$)? (Atomic mass of N = $14 \text{ u}$; Avogadro's number $N_A \approx 6.02 \times 10^{23} \text{ mol}^{-1}$)
A)
$3.01 \times 10^{22}$
B)
$1.505 \times 10^{22}$
C)
$6.02 \times 10^{23}$
D)
$0.05$
E)
$0.1$
Theme: Stoichiometry - Moles and Avogadro's Number
Explanation:
1. Find the molar mass of $\ce{N_2}$:
* The atomic mass of N is $14 \text{ u}$, so the molar mass of $\ce{N_2}$ (a diatomic molecule) is $2 \times 14 \text{ g/mol} = 28 \text{ g/mol}$.
2. Find moles of $\ce{N_2}$:
* $\text{Moles} = \frac{\text{mass}}{\text{Molar Mass}} = \frac{0.7 \text{ g}}{28 \text{ g/mol}} = 0.025 \text{ mol of } \ce{N_2}$
3. Find molecules of $\ce{N_2}$:
* $\text{Molecules} = \text{moles} \times N_A = 0.025 \text{ mol} \times (6.02 \times 10^{23} \text{ molecules/mol}) \approx 1.505 \times 10^{22} \text{ molecules of } \ce{N_2}$
4. Find atoms of N:
* Each $\ce{N_2}$ molecule contains 2 nitrogen atoms.
* $\text{Atoms} = \text{Molecules} \times 2 = (1.505 \times 10^{22}) \times 2 = 3.01 \times 10^{22} \text{ atoms of N}$
Why other options are incorrect:
- B) $1.505 \times 10^{22}$: This is the number of molecules of $\ce{N_2}$, not the number of atoms of N.
- C) $6.02 \times 10^{23}$: This is Avogadro's number, representing 1 mole of atoms, not 0.05 moles.
- D) $0.05$: This is the total moles of N atoms ($0.025 \times 2$), not the number of atoms.
- E) $0.1$: This might result from an incorrect mole calculation.
Answer:→A) $3.01 \times 10^{22}$
45
45. Given the reaction $\ce{C + O_2 -> CO_2}$, how many grams of $\ce{CO_2}$ are produced from the complete combustion of $9 \text{ g}$ of Carbon (C)? (Atomic masses: C = $12 \text{ u}$; O = $16 \text{ u}$)
A)
$33 \text{ g}$
B)
$9 \text{ g}$
C)
$44 \text{ g}$
D)
$2.75 \text{ g}$
E)
$24 \text{ g}$
Theme: Stoichiometry - Mass-Mass Calculations
Explanation:
The balanced equation is $\ce{C + O_2 -> CO_2}$. This shows a 1:1 molar ratio between C and $\ce{CO_2}$.
1. Find molar masses:
* $\text{Molar Mass of C} = 12 \text{ g/mol}$
* $\text{Molar Mass of } \ce{CO_2} = 12 + (2 \times 16) = 44 \text{ g/mol}$
2. Find moles of C:
* $\text{Moles of C} = \frac{\text{mass}}{\text{Molar Mass}} = \frac{9 \text{ g}}{12 \text{ g/mol}} = 0.75 \text{ mol of C}$
3. Find moles of $\ce{CO_2}$ produced:
* Due to the 1:1 ratio, $0.75 \text{ mol of C}$ will produce $0.75 \text{ mol of } \ce{CO_2}$.
4. Find mass of $\ce{CO_2}$:
* $\text{Mass} = \text{moles} \times \text{Molar Mass} = 0.75 \text{ mol} \times 44 \text{ g/mol} = 33 \text{ g}$
Why other options are incorrect:
- B) $9 \text{ g}$: This assumes mass is conserved 1:1, which is incorrect. Moles are conserved in the ratio, not mass.
- C) $44 \text{ g}$: This would be the mass produced if $1 \text{ mole}$ ($12 \text{ g}$) of C reacted.
- D) $2.75 \text{ g}$: This might result from an inverted calculation ($9 \times 12 / 44$).
- E) $24 \text{ g}$: This might result from $0.75 \times 32$ (mass of $\ce{O_2}$ needed).
Answer:→A) $33 \text{ g}$
46
46. How many mL of water must be added to $1 \text{ mL}$ of a strong acid solution with $\text{pH} = 2$ to obtain a solution with $\text{pH} = 4$?
A)
$99 \text{ mL}$
B)
$9 \text{ mL}$
C)
$100 \text{ mL}$
D)
$10 \text{ mL}$
E)
$2 \text{ mL}$
Theme: Acids and Bases - pH and Dilution
Explanation:
1. Find initial and final concentrations:
* $\text{pH} = -\log[\ce{H^+}]$, so $[\ce{H^+}] = 10^{-\text{pH}}$
* Initial: $\text{pH}_1 = 2 \Rightarrow [\ce{H^+}]_1 = M_1 = 10^{-2} \text{ M}$
* Final: $\text{pH}_2 = 4 \Rightarrow [\ce{H^+}]_2 = M_2 = 10^{-4} \text{ M}$
2. Use the dilution formula $M_1V_1 = M_2V_2$:
* $V_1 = 1 \text{ mL}$
* $(10^{-2} \text{ M}) \times (1 \text{ mL}) = (10^{-4} \text{ M}) \times V_2$
* $V_2 = \frac{10^{-2}}{10^{-4}} \times 1 \text{ mL} = 10^2 \times 1 \text{ mL} = 100 \text{ mL}$
3. Find volume of water to add:
$V_2$ is the final* total volume.
* $V_{\text{add}} = V_2 - V_1 = 100 \text{ mL} - 1 \text{ mL} = 99 \text{ mL}$
This means the solution was diluted 100-fold.
Why other options are incorrect:
- B) $9 \text{ mL}$: This would only dilute the solution 10-fold (to $V_2 = 10 \text{ mL}$), resulting in a pH of 3, not 4.
- C) $100 \text{ mL}$: This is the final volume, not the volume of water added.
- D) $10 \text{ mL}$: This is the final volume for a 10-fold dilution.
- E) $2 \text{ mL}$: This is the difference in pH values, not a volume.
Answer:→A) $99 \text{ mL}$
47
47. According to the Brønsted-Lowry theory, a strong acid:
A)
forms a weak conjugate base.
B)
forms a strong conjugate base.
C)
is a poor proton donor.
D)
is a good proton acceptor.
E)
must be in an aqueous solution.
Theme: Acid-Base Theories - Brønsted-Lowry
Explanation:
The Brønsted-Lowry theory defines an acid as a proton ($\ce{H^+}$) donor and a base as a proton acceptor.
* $\text{Acid} + \text{Base} \Leftrightarrow \text{Conjugate Base} + \text{Conjugate Acid}$
A strong acid is a species that readily donates protons (its equilibrium lies far to the right). This implies that its conjugate base (the species left after the proton is donated) has very little tendency to accept the proton back. A species that does not readily accept protons is, by definition, a weak base.
Example: $\ce{HCl}$ (strong acid) $\rightarrow \ce{H^+} + \ce{Cl^-}$ (weak conjugate base)
Why other options are incorrect:
- B) forms a strong conjugate base: This is incorrect. A weak acid forms a relatively strong conjugate base.
- C) is a poor proton donor: This is the definition of a weak acid.
- D) is a good proton acceptor: This is the definition of a strong base.
- E) must be in an aqueous solution: This is a requirement for the Arrhenius theory, not the Brønsted-Lowry theory, which can apply to non-aqueous systems.
Answer:→A) forms a weak conjugate base.
48
48. What is the simplified value of the expression $(\sqrt[3]{512})^{1/2}$?
A)
$2\sqrt{2}$
B)
$8$
C)
$4$
D)
$2^{1/6}$
E)
$512^{2/3}$
Theme: Exponents and Radicals
Explanation:
The expression can be rewritten using fractional exponents:
$(\sqrt[3]{512})^{1/2} = (512^{1/3})^{1/2}$
Using the power of a power rule ($(x^a)^b = x^{a \times b}$):
$= 512^{(1/3) \times (1/2)} = 512^{1/6}$
Now, we need to find the prime factorization of 512. We know $2^9 = 512$.
Substitute this back into the expression:
$(2^9)^{1/6} = 2^{9 \times (1/6)} = 2^{9/6} = 2^{3/2}$
To simplify $2^{3/2}$:
$2^{3/2} = 2^{1 + 1/2} = 2^1 \times 2^{1/2} = 2\sqrt{2}$
Why other options are incorrect:
- B) $8$: This is the value of $\sqrt[3]{512}$ ($8^3 = 512$), but it neglects the final $1/2$ exponent.
- C) $4$: This would be $2^2$.
- D) $2^{1/6}$: This would be correct if $512 = 2^1$.
- E) $512^{2/3}$: This inverts the exponents.
Answer:→A) $2\sqrt{2}$
49
49. Given the function $f(x)= \log_2(x^2 + 12)$, what is the reciprocal of $f(2)$?
A)
$\frac{1}{4}$
B)
$4$
C)
$\log_2(16)$
D)
$-\frac{1}{4}$
E)
$16$
Theme: Functions and Logarithms
Explanation:
1. Evaluate the function at $x=2$:
$f(2) = \log_2(2^2 + 12)$
$f(2) = \log_2(4 + 12)$
$f(2) = \log_2(16)$
2. Solve the logarithm:
We need to find the power $y$ such that $2^y = 16$.
Since $2^4 = 16$, we have $\log_2(16) = 4$.
So, $f(2) = 4$.
3. Find the reciprocal:
The reciprocal of a number $y$ is $\frac{1}{y}$.
The reciprocal of $f(2) = 4$ is $\frac{1}{4}$.
Why other options are incorrect:
- B) $4$: This is the value of $f(2)$, not its reciprocal.
- C) $\log_2(16)$: This is also the value of $f(2)$, just unevaluated.
- D) $-\frac{1}{4}$: This is the negative reciprocal.
- E) $16$: This is the argument of the logarithm, not its value.
Answer:→A) $\frac{1}{4}$
50
50. A bag contains 3 red balls and 7 green balls. What is the probability of drawing two green balls in two consecutive extractions, assuming the draws are independent (i.e., with replacement)?
A)
$\frac{49}{100}$
B)
$\frac{7}{10}$
C)
$\frac{42}{90}$
D)
$\frac{21}{100}$
E)
$\frac{9}{100}$
Theme: Probability - Independent Events
Explanation:
1. Find the total number of balls:
Total = $3 \text{ red} + 7 \text{ green} = 10 \text{ balls}$
2. Find the probability of drawing one green ball:
$P(\text{Green}) = \frac{\text{Number of green balls}}{\text{Total number of balls}} = \frac{7}{10}$
3. Calculate the probability of two independent events:
The problem implies independent draws (or drawing with replacement). The probability of two independent events (A and B) occurring is $P(A \text{ and } B) = P(A) \times P(B)$.
$P(\text{Green then Green}) = P(\text{Green on 1st}) \times P(\text{Green on 2nd})$
$P(GG) = \left(\frac{7}{10}\right) \times \left(\frac{7}{10}\right) = \frac{49}{100}$
Why other options are incorrect:
- B) $\frac{7}{10}$: This is the probability of drawing only one green ball.
- C) $\frac{42}{90}$: This would be the probability without replacement ($\frac{7}{10} \times \frac{6}{9}$).
- D) $\frac{21}{100}$: This might result from $\frac{3}{10} \times \frac{7}{10}$ (probability of Red then Green).
- E) $\frac{9}{100}$: This would be the probability of drawing two red balls ($\frac{3}{10} \times \frac{3}{10}$).
Answer:→A) $\frac{49}{100}$
51
51. What is the solution to the inequality $\frac{x^2 + |4x + 3|}{4 - 3x} \geq 0$?
A)
$x < \frac{4}{3}$
B)
$x > \frac{4}{3}$
C)
$x \geq -\frac{3}{4}$
D)
$x = 0$
E)
All real numbers
Theme: Solving Inequalities
Explanation:
We need to solve $\frac{N(x)}{D(x)} \geq 0$, where $N(x) = x^2 + |4x + 3|$ and $D(x) = 4 - 3x$.
1. Analyze the Numerator, $N(x)$:
* $x^2$ is always non-negative ($x^2 \geq 0$).
* $|4x + 3|$ (an absolute value) is also always non-negative ($|4x + 3| \geq 0$).
* The sum of two non-negative terms $N(x) = x^2 + |4x + 3|$ is also non-negative ($N(x) \geq 0$).
Can $N(x) = 0$? This would require $x^2 = 0$ (so $x=0$) AND $|4x + 3| = 0$ (so $x=-3/4$). Since $x$ cannot be both $0$ and $-3/4$ simultaneously, the numerator is never* zero. It is always strictly positive ($N(x) > 0$).
2. Analyze the Inequality:
Since the numerator is always positive, for the fraction $\frac{\text{Positive}}{D(x)} \geq 0$, the denominator $D(x)$ must also be positive.
* Note: $D(x)$ cannot be zero, as division by zero is undefined. So we must have $D(x) > 0$.
3. Solve for $D(x) > 0$:
$4 - 3x > 0$
$4 > 3x$
$\frac{4}{3} > x$, which is the same as $x < \frac{4}{3}$.
Why other options are incorrect:
- B) $x > \frac{4}{3}$: This would make the denominator negative, and the whole fraction negative.
- C) $x \geq -\frac{3}{4}$: This range includes values (like $x=2$) that make the denominator negative.
- D) $x = 0$: This is one solution, but not the complete solution set.
- E) All real numbers: This is incorrect, as any $x \geq \frac{4}{3}$ is not a solution.
Answer:→A) $x < \frac{4}{3}$
52
52. In a circle, $\theta$ is the acute angle formed between the tangent at point A and the chord AB. $\phi$ is the angle $\angle BDA$, where D is a point on the major arc AB. What is the relationship between $\phi$ and $\theta$?
A)
$\phi = \theta$
B)
$\phi = 2\theta$
C)
$\theta = 2\phi$
D)
$\phi + \theta = 90^\circ$
E)
$\phi + \theta = 180^\circ$
Theme: Circle Geometry - Alternate Segment Theorem
Explanation:
This question describes the Alternate Segment Theorem.
* $\theta$ is the angle between the tangent (at A) and the chord (AB).
$\phi = \angle BDA$ is the inscribed angle subtended by the chord AB in the alternate segment* (the major arc).
The Alternate Segment Theorem states that the angle between a tangent and a chord through the point of contact is equal to the angle in the alternate segment.
Therefore, $\phi = \theta$.
Why other options are incorrect:
- B) $\phi = 2\theta$ & C) $\theta = 2\phi$: The 2:1 relationship is between the central angle and the inscribed angle, which are not described here.
- D) $\phi + \theta = 90^\circ$: This would only be true in a special case, such as if the chord AB formed a $45^\circ$ angle with the tangent.
- E) $\phi + \theta = 180^\circ$: This describes the relationship for opposite angles in a cyclic quadrilateral, which doesn't apply here.
Answer:→A) $\phi = \theta$
53
53. What is the volume of a cylinder with a base radius $r$ and height $h$, if $r^2 = 25 \text{ cm}^2$ and $h = 7 \text{ cm}$?
A)
$175\pi \text{ cm}^3$
B)
$35\pi \text{ cm}^3$
C)
$125\pi \text{ cm}^3$
D)
$25\pi \text{ cm}^3$
E)
$175 \text{ cm}^3$
Theme: Geometry - Volume of a Cylinder
Explanation:
The formula for the volume $V$ of a cylinder is:
$V = (\text{Area of Base}) \times \text{Height}$
The base is a circle, so its area is $A = \pi r^2$.
$V = \pi r^2 h$
We are given the values for $r^2$ and $h$ directly:
* $r^2 = 25 \text{ cm}^2$
* $h = 7 \text{ cm}$
Substitute these values into the formula:
$V = \pi (25 \text{ cm}^2) (7 \text{ cm}) = 175\pi \text{ cm}^3$
Why other options are incorrect:
- B) $35\pi \text{ cm}^3$: This might result from $5 \times 7 \times \pi$ (using $r=5$ instead of $r^2$).
- C) $125\pi \text{ cm}^3$: This might result from $25 \times 5 \times \pi$ (using $r^2 \times r$).
- D) $25\pi \text{ cm}^3$: This is the area of the base, not the volume.
- E) $175 \text{ cm}^3$: This omits the $\pi$ from the formula.
Answer:→A) $175\pi \text{ cm}^3$
54
54. In a right triangle, $a$ and $b$ are the lengths of the two legs (cathetus), and $c$ is the length of the hypotenuse. If $\alpha$ is the angle opposite leg $a$, which expression is correct?
A)
$a = c \sin(\alpha)$
B)
$a = c \cos(\alpha)$
C)
$a = b \sin(\alpha)$
D)
$c = a \sin(\alpha)$
E)
$a = c \tan(\alpha)$
Theme: Trigonometry - SOH CAH TOA
Explanation:
The basic trigonometric definitions in a right triangle are (SOH CAH TOA):
* $\sin(\text{angle}) = \frac{\text{Opposite}}{\text{Hypotenuse}}$
* $\cos(\text{angle}) = \frac{\text{Adjacent}}{\text{Hypotenuse}}$
* $\tan(\text{angle}) = \frac{\text{Opposite}}{\text{Adjacent}}$
In this problem:
* The angle is $\alpha$.
The Opposite* side is $a$.
The Hypotenuse* is $c$.
Using the sine definition (SOH):
$\sin(\alpha) = \frac{a}{c}$
To solve for $a$, we multiply both sides by $c$:
$a = c \sin(\alpha)$
Why other options are incorrect:
- B) $a = c \cos(\alpha)$: $\cos(\alpha)$ relates the adjacent side ($b$) and hypotenuse ($c$), so $b = c \cos(\alpha)$.
- C) $a = b \sin(\alpha)$: This incorrectly mixes the sine ratio.
- D) $c = a \sin(\alpha)$: This is an incorrect rearrangement of the formula.
- E) $a = c \tan(\alpha)$: $\tan(\alpha)$ relates the opposite ($a$) and adjacent ($b$), so $a = b \tan(\alpha)$.
Answer:→A) $a = c \sin(\alpha)$
55
55. A constant braking force $F = 210 \text{ N}$ is applied to an object over a distance $s = 5 \text{ m}$. Which of the following is required to calculate the power $P$ exerted by this force?
A)
The time $t$ over which the force was applied, or the speed $v$ of the object.
B)
The mass $m$ of the object.
C)
The initial speed $v_0$ of the object only.
D)
The final speed $v_f$ of the object only.
E)
No additional information is needed.
Theme: Work, Energy, and Power
Explanation:
This question was deemed flawed in the original test because it asked for a numerical answer that was impossible to calculate. The core issue is the definition of power.
Power ($P$) is the rate at which work ($W$) is done.
$P = \frac{W}{t}$
Work done by a constant force is $W = Fs$.
So, $P = \frac{Fs}{t}$.
We are given $F$ ($210 \text{ N}$) and $s$ ($5 \text{ m}$), but we do not know the time $t$.
Alternatively, if the force is applied to an object moving at speed $v$, the power is $P = Fv$. We do not know $v$.
Therefore, to calculate the power, we need either the time $t$ or the speed $v$. (If $v$ is not constant, $P = Fv$ gives instantaneous power, while $P = W/t$ gives average power).
Why other options are incorrect:
- B) The mass $m$ of the object: Mass would be needed to find acceleration ($a = F/m$), but not power directly.
- C) & D) Initial or final speed only: Knowing just one speed isn't enough to find $t$ or the average speed without knowing the acceleration (which requires mass).
- E) No additional information is needed: This is incorrect, as $t$ or $v$ is missing.
Answer:→A) The time $t$ over which the force was applied, or the speed $v$ of the object.
56
56. An ideal gas is at an initial state with pressure $P$ and volume $V$. If the volume is tripled to $3V$ while the temperature remains constant, what is the new pressure $P'$?
A)
$\frac{P}{3}$
B)
$3P$
C)
$P$
D)
$\frac{P}{9}$
E)
$9P$
Theme: Gas Laws - Boyle's Law
Explanation:
This scenario describes an isothermal (constant temperature) process for an ideal gas.
Boyle's Law states that for a fixed amount of gas at constant temperature, pressure and volume are inversely proportional.
$P_1 V_1 = P_2 V_2$
Given:
* $P_1 = P$
* $V_1 = V$
* $V_2 = 3V$
* $P_2 = P'$
Substitute the values:
$P \times V = P' \times (3V)$
Divide both sides by $3V$ to solve for $P'$:
$P' = \frac{PV}{3V} = \frac{P}{3}$
Tripling the volume at constant temperature reduces the pressure to one-third of its original value.
Why other options are incorrect:
- B) $3P$: This would happen if the volume was reduced to $V/3$.
- C) $P$: The pressure only stays constant if the volume also stays constant (at constant T).
- D) & E): The 9:1 ratio relates to squared terms, which are not relevant here.
Answer:→A) $\frac{P}{3}$
57
57. A conductor dissipates $P = 2922 \text{ W}$ of power when a current $I = 10 \text{ A}$ flows through it. What is the resistance $R$ of the conductor?
A)
$29.22 \Omega$
B)
$292.2 \Omega$
C)
$2.922 \Omega$
D)
$29220 \Omega$
E)
$0.0034 \Omega$
Theme: Electric Circuits - Joule's Law (Power)
Explanation:
The relationship between power ($P$), current ($I$), and resistance ($R$) is given by Joule's Law of heating:
$P = I^2 R$
We are given $P$ and $I$ and need to find $R$.
Given:
* $P = 2922 \text{ W}$
* $I = 10 \text{ A}$
Rearrange the formula to solve for $R$:
$R = \frac{P}{I^2}$
Substitute the values:
$R = \frac{2922 \text{ W}}{(10 \text{ A})^2} = \frac{2922 \text{ W}}{100 \text{ A}^2}$
$R = 29.22 \Omega$
Why other options are incorrect:
- B) $292.2 \Omega$: This would be the result of $P / I$, which is Voltage ($V$), not Resistance.
- C) $2.922 \Omega$: This is off by a factor of 10.
- D) $29220 \Omega$: This is the result of $P \times I$, which is not a standard formula.
- E) $0.0034 \Omega$: This is the result of $I^2 / P$, the inverse of the correct calculation.
Answer:→A) $29.22 \Omega$
58
58. An electron enters a uniform magnetic field $\vec{B}$ at a velocity $\vec{v}$ that is perpendicular to $\vec{B}$. Which of the following statements about the electron's motion is FALSE?
A)
The electron moves with a constant velocity $\vec{v}$.
B)
The radius of its path is $r = \frac{m_e v}{e B}$.
C)
The period of its motion is $T = \frac{2 \pi m_e}{e B}$.
D)
The angular velocity of its motion is $\omega = \frac{e B}{m_e}$.
E)
The magnetic force provides the centripetal acceleration.
Theme: Electromagnetism - Charged Particle in a Magnetic Field
Explanation:
1.  Force: The magnetic (Lorentz) force $\vec{F} = q(\vec{v} \times \vec{B})$ is always perpendicular to the velocity $\vec{v}$.
2.  Work and Speed: Since the force is always perpendicular to the direction of motion, it does no work ($W = 0$). By the work-energy theorem, the kinetic energy ($KE = \frac{1}{2}m_e v^2$) and thus the speed $v$ (magnitude of velocity) remain constant.
3.  Velocity: Because the force is perpendicular, it continuously changes the direction of the velocity vector. Since the direction changes, the velocity vector $\vec{v}$ is NOT constant. A constant velocity requires both constant speed and constant direction.
4.  Motion: This constant-magnitude perpendicular force acts as a centripetal force ($F_c = \frac{m_e v^2}{r}$), causing the electron to move in a uniform circular path.
* $F_B = F_c \Rightarrow e v B = \frac{m_e v^2}{r} \Rightarrow r = \frac{m_e v}{e B}$. (Statement B is true).
* $\omega = \frac{v}{r} = \frac{v}{(\frac{m_e v}{e B})} = \frac{e B}{m_e}$. (Statement D is true).
* $T = \frac{2\pi}{\omega} = \frac{2 \pi m_e}{e B}$. (Statement C is true).
The magnetic force is* the net force providing the centripetal acceleration. (Statement E is true).
Therefore, statement A is false.
Answer:→A) The electron moves with a constant velocity $\vec{v}$.
59
59. The position of a particle in oscillatory motion is given by $x(t) = 4 \cos(\omega t)$, with angular frequency $\omega = 2\pi \text{ rad/s}$. What is the velocity of the particle at $t = \frac{1}{2} \text{ s}$?
A)
$0 \text{ m/s}$
B)
$-8\pi \text{ m/s}$
C)
$4 \text{ m/s}$
D)
$-4 \text{ m/s}$
E)
$8\pi \text{ m/s}$
Theme: Simple Harmonic Motion (SHM)
Explanation:
1. Find the velocity function $v(t)$:
Velocity is the first derivative of position $x(t)$ with respect to time $t$.
$v(t) = \frac{dx}{dt} = \frac{d}{dt} [4 \cos(\omega t)]$
Using the chain rule: $v(t) = 4 \times [-\sin(\omega t) \times \omega] = -4\omega \sin(\omega t)$
2. Substitute the value of $\omega = 2\pi$:
$v(t) = -4(2\pi) \sin(2\pi t) = -8\pi \sin(2\pi t)$
3. Calculate velocity at $t = \frac{1}{2} \text{ s}$:
$v(\frac{1}{2}) = -8\pi \sin(2\pi \times \frac{1}{2}) = -8\pi \sin(\pi)$
4. Evaluate $\sin(\pi)$:
The sine of $\pi$ radians ($180^\circ$) is $0$.
$v(\frac{1}{2}) = -8\pi \times (0) = 0 \text{ m/s}$
(This makes physical sense: at $t=T/2 = 1/2 \text{ s}$, the particle has completed half an oscillation and is momentarily at rest at the other extreme position $x=-4$).
Why other options are incorrect:
- B) $-8\pi \text{ m/s}$: This is the maximum speed, which occurs when $\sin(2\pi t) = 1$ (e.g., at $t=1/4 \text{ s}$).
- C) $4 \text{ m/s}$: This is the amplitude of position.
- D) $-4 \text{ m/s}$: This is the position $x(t)$ at $t=1/2 \text{ s}$, not the velocity.
- E) $8\pi \text{ m/s}$: This is the magnitude of the maximum speed.
Answer:→A) $0 \text{ m/s}$
60
60. Which of the following statements about the motion of a simple pendulum is FALSE?
A)
Without friction, a pendulum stops after a few oscillations.
B)
Without friction (and for small angles), the motion is simple harmonic oscillation.
C)
With friction, the motion is a damped oscillatory motion.
D)
The pendulum stops momentarily at the highest point of its swing.
E)
The pendulum bob moves along a circular arc.
Theme: Simple Harmonic Motion - Pendulum
Explanation:
Let's analyze the physics of a simple pendulum.
B) Simple Harmonic Motion: For small angles of displacement, the restoring force is approximately proportional to the displacement ($F \approx -mg\theta$). This condition leads to Simple Harmonic Motion (SHM). This statement is true*.
C) Damped Motion: In a real-world scenario, friction (air resistance) is a dissipative force that removes energy from the system, causing the amplitude of the oscillations to decrease over time. This is called damped oscillation. This statement is true*.
D) Highest Point: At the peak (maximum amplitude) of its swing, the pendulum's kinetic energy is zero, and its potential energy is maximum. It is momentarily at rest before reversing direction. This statement is true*.
E) Circular Arc: The pendulum bob is fixed by a string of constant length $L$, so it swings along the arc of a circle with radius $L$. This statement is true*.
A) No Friction: In an ideal, frictionless system (in a vacuum), mechanical energy is conserved. The pendulum would never lose energy and would continue to oscillate indefinitely. Therefore, the statement that it stops is false*.
Answer:→A) Without friction, a pendulum stops after a few oscillations.

Section Review

Biology

A total of 23 questions primarily focused on cell biology, genetics, and molecular topics.
Questions were straightforward, requiring knowledge of fundamental concepts.
Simplified compared to prior years, with no anatomy or physiology questions, making Biology the easiest section this year.

Chemistry

Consisted of 15 questions, with topics like the mole concept, properties of gases, and acids and bases being heavily emphasized.
Difficulty was moderate but decisive for student rankings due to its balanced design.
A strong performance in Chemistry was crucial for distinguishing oneself.

Physics

Included 6 questions covering kinematics, thermodynamics, and electromagnetism.
Key topics involved electron motion in magnetic fields and simple harmonic motion.
While varied, it was approachable for those with a solid understanding of fundamental formulas and applications.

Mathematics

Featured 7 questions focusing on algebra, geometry, and probability.
Geometry and algebra were core scoring areas, with moderate difficulty levels.
Understanding key formulas and properties (e.g., logarithms and circles) was vital for success.