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Question 1General Biology

Which organelle is the primary site of ATP production via oxidative phosphorylation in a eukaryotic cell?

  1. Golgi apparatus
  2. Ribosome
  3. Lysosome
  4. Mitochondrion Correct answer.

Explanation

The inner mitochondrial membrane houses the electron transport chain and ATP synthase, which together carry out oxidative phosphorylation. Ribosomes synthesize proteins, the Golgi modifies and sorts them, and lysosomes degrade material, so none of these generate ATP on that scale.

Question 2General Biology

During DNA replication, which enzyme adds nucleotides to the growing strand by extending an existing primer?

  1. Topoisomerase
  2. DNA ligase
  3. DNA polymerase Correct answer.
  4. Helicase

Explanation

DNA polymerase reads the template strand and adds complementary deoxynucleotides to the 3' end of a primer. Ligase joins nicks, helicase unwinds the duplex, and topoisomerase relieves supercoiling ahead of the fork.

Question 3General Biology

A cell placed in a hypertonic solution will most likely:

  1. Actively pump water inward
  2. Lose water and shrink Correct answer.
  3. Swell and possibly lyse
  4. Show no net water movement

Explanation

In a hypertonic environment the solute concentration outside exceeds that inside, so water leaves the cell by osmosis and the cell shrinks. Swelling occurs in hypotonic solutions, and water movement is passive rather than actively pumped.

Question 4General Biology

Which molecule serves as the direct energy currency that powers most cellular work?

  1. Glucose
  2. ATP Correct answer.
  3. NADH
  4. FADH2

Explanation

ATP hydrolysis releases free energy that drives endergonic reactions such as transport and biosynthesis. NADH and FADH2 are electron carriers that feed the electron transport chain, and glucose is a fuel that must be catabolized first.

Question 5General Biology

In Mendelian genetics, a cross between two heterozygotes (Aa x Aa) is expected to produce which phenotypic ratio for a completely dominant trait?

  1. 1:2:1
  2. 1:1
  3. 3:1 Correct answer.
  4. 9:3:3:1

Explanation

Two heterozygotes produce offspring in a genotypic ratio of 1 AA : 2 Aa : 1 aa. Because the dominant allele masks the recessive in heterozygotes, the phenotypic ratio collapses to 3 dominant : 1 recessive.

Question 6General Biology

Which process produces genetically diverse haploid cells from a diploid precursor?

  1. Meiosis Correct answer.
  2. Binary fission
  3. Mitosis
  4. Budding

Explanation

Meiosis involves two divisions with crossing over and independent assortment, halving the chromosome number and generating genetic variation. Mitosis and budding produce genetically identical diploid cells, and binary fission is prokaryotic replication.

Question 7General Biology

Which of the following best describes the role of tRNA during translation?

  1. It forms the structural core of the ribosome
  2. It carries the genetic message from DNA to the ribosome
  3. It delivers amino acids matching the mRNA codon Correct answer.
  4. It catalyzes peptide bond formation

Explanation

Each tRNA carries a specific amino acid and has an anticodon that base-pairs with the complementary mRNA codon, positioning the amino acid for incorporation. mRNA carries the message, rRNA catalyzes peptide bonds, and ribosomal proteins form the core.

Question 8General Biology

Which type of bond links adjacent amino acids in a polypeptide chain?

  1. Hydrogen bond
  2. Peptide bond Correct answer.
  3. Ionic bond
  4. Phosphodiester bond

Explanation

A peptide bond forms by a dehydration reaction between the carboxyl group of one amino acid and the amino group of the next. Phosphodiester bonds link nucleotides, hydrogen bonds stabilize secondary structure, and ionic interactions occur between charged side chains.

Question 9General Biology

A mutation changes a single nucleotide but the resulting protein has the same amino acid sequence. This mutation is best described as:

  1. Nonsense
  2. Silent Correct answer.
  3. Frameshift
  4. Missense

Explanation

Because the genetic code is degenerate, several codons specify the same amino acid, so a substitution can leave the sequence unchanged. Missense changes one amino acid, nonsense creates a stop codon, and frameshift alters the reading frame.

Question 10General Biology

During which phase of the cell cycle does DNA replication occur?

  1. G2 phase
  2. G1 phase
  3. M phase
  4. S phase Correct answer.

Explanation

DNA synthesis takes place during S phase, which lies between the two gap phases. G1 involves growth, G2 involves further growth and preparation for division, and M phase is when chromosomes segregate and the cell divides.

Question 11General Biology

In the light-dependent reactions of photosynthesis, what is the primary source of electrons that ultimately reduces NADP+?

  1. Glucose
  2. Carbon dioxide
  3. ATP
  4. Water Correct answer.

Explanation

Photosystem II splits water to replace the electrons it donates to the electron transport chain, releasing oxygen as a byproduct. These electrons flow through the chain to NADP+, reducing it to NADPH. Carbon dioxide is fixed later in the Calvin cycle.

Question 12General Biology

Enzyme activity typically increases with temperature up to a point, then declines sharply. What best explains the decline?

  1. Competitive inhibitors accumulate
  2. The enzyme's activation energy increases
  3. Substrate concentration becomes limiting
  4. The enzyme denatures as hydrogen bonds and other interactions break Correct answer.

Explanation

Excess heat disrupts the noncovalent interactions maintaining tertiary structure, denaturing the active site so substrate can no longer bind. Substrate limitation and inhibitor accumulation do not explain the temperature-dependent collapse of activity.

Question 13General Biology

A woman who is a carrier for an X-linked recessive disorder has children with an unaffected man. What proportion of their sons is expected to be affected?

  1. 25%
  2. 0%
  3. 50% Correct answer.
  4. 100%

Explanation

Sons inherit their single X chromosome from the mother, and a carrier mother transmits the affected allele to half of her sons. Because males are hemizygous, inheriting the mutant allele is sufficient to express the disorder.

Question 14General Biology

Which feature distinguishes prokaryotic from eukaryotic cells?

  1. Prokaryotes lack a membrane-bound nucleus Correct answer.
  2. Prokaryotes lack ribosomes
  3. Prokaryotes lack nucleic acids
  4. Prokaryotes lack a plasma membrane

Explanation

Prokaryotes keep their DNA in a nucleoid region without a nuclear envelope, whereas eukaryotes enclose chromosomes in a nucleus. Prokaryotes still possess ribosomes, a plasma membrane, and DNA, so those options are incorrect.

Question 15General Biology

In a population at Hardy-Weinberg equilibrium, the frequency of a recessive allele is 0.2. What is the expected frequency of heterozygous individuals?

  1. 0.32 Correct answer.
  2. 0.16
  3. 0.04
  4. 0.64

Explanation

With q = 0.2, p = 0.8, and the heterozygote frequency is 2pq = 2(0.8)(0.2) = 0.32. The value 0.04 equals q squared and 0.64 equals p squared, which are homozygote frequencies.

Question 16General Biology

Which statement best describes the function of the sodium-potassium pump?

  1. It transports only sodium ions across the membrane
  2. It uses ATP to move three sodium ions out and two potassium ions in Correct answer.
  3. It moves potassium out and sodium in using ATP
  4. It moves sodium and potassium down their gradients without energy input

Explanation

The pump hydrolyzes ATP to export three Na+ ions and import two K+ ions against their gradients, maintaining the resting membrane potential. Because it moves ions against their gradients, it requires energy and is electrogenic.

Question 17General Biology

Aerobic respiration and fermentation both begin with glycolysis, but they differ in that fermentation:

  1. Completely oxidizes glucose to carbon dioxide
  2. Produces more ATP per glucose than aerobic respiration
  3. Regenerates NAD+ so glycolysis can continue without oxygen Correct answer.
  4. Occurs only in the mitochondria

Explanation

Without oxygen, the electron transport chain cannot reoxidize NADH, so fermentation reduces pyruvate or its derivatives to regenerate NAD+ and sustain glycolysis. Fermentation yields far less ATP than aerobic respiration and occurs in the cytosol.

Question 18General Biology

Which of the following correctly describes the relationship between a codon and an anticodon?

  1. Both are sequences on the DNA template strand
  2. The codon is on tRNA and the anticodon is on rRNA
  3. Both are found on the same tRNA molecule
  4. The codon is on mRNA and the anticodon is on tRNA Correct answer.

Explanation

A codon is a three-base sequence on mRNA that specifies an amino acid, while the anticodon is the complementary three-base sequence on tRNA that pairs with it. Base pairing between them positions the correct amino acid in the ribosome.

Question 19General Biology

In a dihybrid cross between two individuals heterozygous for both genes (AaBb x AaBb), assuming independent assortment, what fraction of offspring is expected to show both recessive traits?

  1. 1/4
  2. 9/16
  3. 1/16 Correct answer.
  4. 3/16

Explanation

Each recessive trait appears in one quarter of offspring from a monohybrid cross, and independent assortment lets the probabilities multiply: 1/4 x 1/4 = 1/16. The 3/16 and 9/16 values correspond to other phenotype classes in the 9:3:3:1 ratio.

Question 20General Biology

A competitive inhibitor affects an enzyme reaction in which way?

  1. It raises the apparent Km without changing Vmax Correct answer.
  2. It lowers Vmax irreversibly
  3. It binds the enzyme-substrate complex only
  4. It lowers both Km and Vmax

Explanation

A competitive inhibitor binds the free enzyme at the active site, so more substrate is needed to reach half-maximal velocity, raising the apparent Km. Because sufficiently high substrate can outcompete the inhibitor, Vmax is unchanged.

Question 21General Biology

Which observation would most directly support the endosymbiotic theory for the origin of mitochondria?

  1. Mitochondria produce ATP through chemiosmosis
  2. Mitochondria are present in all eukaryotic cells
  3. Mitochondria contain their own circular DNA and ribosomes resembling bacterial ones Correct answer.
  4. Mitochondria are enclosed by a double membrane

Explanation

Circular DNA and bacteria-like ribosomes inside mitochondria indicate descent from a free-living prokaryote, which is the core evidence for endosymbiosis. A double membrane is consistent with engulfment but is less specific than molecular evidence.

Question 22General Biology

A frameshift mutation occurs early in a coding sequence. Which consequence is most likely?

  1. A completely altered downstream amino acid sequence and often a premature stop Correct answer.
  2. A single amino acid substitution with little effect
  3. No change in the protein because the code is degenerate
  4. Duplication of the entire chromosome

Explanation

Inserting or deleting a number of nucleotides not divisible by three shifts the reading frame, so every downstream codon is read differently, usually producing a truncated, nonfunctional protein. Degeneracy buffers substitutions, not frameshifts.

Question 23General Biology

In a signal transduction pathway, a G-protein-coupled receptor is activated by a ligand. What immediately follows receptor activation?

  1. A second messenger enters the nucleus to alter transcription
  2. The receptor is internalized and degraded
  3. The G protein exchanges GDP for GTP and dissociates into active subunits Correct answer.
  4. The receptor directly phosphorylates downstream proteins

Explanation

Ligand binding triggers a conformational change that activates the associated G protein, which swaps GDP for GTP and separates into alpha and beta-gamma subunits that modulate effectors. Direct phosphorylation is characteristic of receptor tyrosine kinases.

Question 24General Biology

A researcher observes that a trait appears in every generation, affects both sexes equally, and an affected individual always has at least one affected parent. Which inheritance pattern is most consistent?

  1. Autosomal dominant Correct answer.
  2. Mitochondrial
  3. X-linked recessive
  4. Autosomal recessive

Explanation

Autosomal dominant traits appear in each generation, affect males and females equally, and require an affected parent for transmission. Autosomal recessive traits often skip generations, X-linked recessive traits affect males disproportionately, and mitochondrial traits pass only through mothers.

Question 25General Biology

Two enzymes catalyze the same reaction but have different Km values. Which statement is correct?

  1. Km is independent of substrate affinity
  2. The enzyme with the higher Km has a greater Vmax
  3. The enzyme with the lower Km reaches half-maximal velocity at a lower substrate concentration Correct answer.
  4. The enzyme with the lower Km always has a higher Vmax

Explanation

Km is the substrate concentration at which the reaction proceeds at half of Vmax, so a lower Km indicates higher apparent affinity for substrate. Km does not determine Vmax, and the two parameters are measured independently.

Question 26General Biology

Which organelle is the primary site of ATP production by oxidative phosphorylation in a eukaryotic cell?

  1. Smooth endoplasmic reticulum
  2. Golgi apparatus
  3. Mitochondrion Correct answer.
  4. Lysosome

Explanation

Oxidative phosphorylation depends on the electron transport chain and ATP synthase embedded in the inner mitochondrial membrane, so the mitochondrion is the main site of this ATP yield. The other listed organelles handle protein sorting, hydrolysis, and lipid synthesis rather than chemiosmotic ATP generation.

Question 27General Biology

A cell placed in a hypertonic solution loses water and shrinks. Which property of the plasma membrane best explains this movement of water?

  1. Its selective permeability to solutes combined with aquaporin channels Correct answer.
  2. Its rigid cellulose wall restricting expansion
  3. Its ability to perform active transport of water molecules
  4. Its complete impermeability to water

Explanation

Water moves by osmosis down its own concentration gradient, crossing the lipid bilayer and aquaporin channels while most solutes cannot follow. In a hypertonic environment the external solute concentration is higher, so net water efflux shrinks the cell.

Question 28General Biology

Which molecule serves as the final electron acceptor at the end of the mitochondrial electron transport chain?

  1. FAD
  2. NAD+
  3. Oxygen Correct answer.
  4. Pyruvate

Explanation

Oxygen accepts electrons from complex IV and combines with protons to form water, which keeps electrons flowing through the chain. NAD+ and FAD are electron carriers that deliver electrons earlier in the process, not terminal acceptors.

Question 29General Biology

In a pedigree, a trait appears only in males, is never passed from father to son, and is transmitted through unaffected carrier mothers. Which mode of inheritance is most consistent with this pattern?

  1. Autosomal dominant
  2. X-linked recessive Correct answer.
  3. Mitochondrial inheritance
  4. Y-linked inheritance

Explanation

X-linked recessive traits affect males far more often because males carry a single X, and affected fathers pass their Y to sons, so father-to-son transmission does not occur. Carrier mothers transmit the allele to half their sons, matching the described pattern.

Question 30General Biology

During DNA replication, which enzyme relieves the supercoiling that builds up ahead of the replication fork?

  1. DNA ligase
  2. Primase
  3. Helicase
  4. Topoisomerase Correct answer.

Explanation

Topoisomerases cut and rejoin DNA strands to relieve torsional stress generated as the fork advances. Without this activity the accumulating supercoils would stall the replication machinery.

Question 31General Biology

A tRNA molecule has the anticodon 5'-AGC-3'. Assuming standard base pairing, which mRNA codon does it recognize?

  1. 5'-CGA-3'
  2. 5'-GCU-3' Correct answer.
  3. 5'-TCG-3'
  4. 5'-AGC-3'

Explanation

Anticodons pair antiparallel with codons, so the anticodon 5'-AGC-3' aligns with the complementary mRNA sequence 3'-UCG-5', which is written 5'-GCU-3'. Codon and anticodon sequences are both read in the conventional 5' to 3' direction, requiring the reversal.

Question 32General Biology

A single gene produces several distinct protein isoforms in different tissues. Which mechanism most directly accounts for this?

  1. Silent mutation within the coding region
  2. Duplication of the centromere
  3. Gene amplification of the locus
  4. Alternative splicing of the pre-mRNA transcript Correct answer.

Explanation

Alternative splicing joins different combinations of exons, so one pre-mRNA can yield multiple mature mRNAs and thus multiple protein isoforms. This is a common route to tissue-specific protein diversity from a single gene.

Question 33General Biology

In a cross between a homozygous red-flowered plant and a homozygous white-flowered plant, all F1 offspring have pink flowers. When the F1 plants are crossed, the F2 shows a 1 red : 2 pink : 1 white ratio. Which genetic phenomenon does this illustrate?

  1. Codominance
  2. Incomplete dominance Correct answer.
  3. Epistasis
  4. Complete dominance

Explanation

In incomplete dominance the heterozygote shows an intermediate phenotype, so the F2 phenotypic ratio matches the genotypic ratio of 1:2:1. No allele fully masks the other, producing the blended pink color.

Question 34General Biology

Which of the following best describes the role of the promoter in gene expression?

  1. It encodes the amino acid sequence of the resulting polypeptide
  2. It carries the amino acids to the ribosome during translation
  3. It specifies the site of polyadenylation of the transcript
  4. It provides a binding site where RNA polymerase and transcription factors assemble Correct answer.

Explanation

A promoter is a regulatory DNA sequence upstream of a gene where RNA polymerase and associated transcription factors bind to initiate transcription. Its sequence and bound factors determine when and how strongly the gene is expressed.

Question 35General Biology

A population of bacteria is exposed to an antibiotic, and a few cells already carry a resistance mutation before exposure. After treatment, nearly all surviving cells are resistant. What best explains this outcome?

  1. The antibiotic selects for pre-existing resistant variants Correct answer.
  2. The bacteria transfer resistance by conjugation only after exposure
  3. The antibiotic induces resistance mutations in each cell
  4. The antibiotic is converted into a nutrient by the bacteria

Explanation

Selection acts on variation that already exists: resistant cells survive and reproduce while susceptible cells die, so the population shifts toward resistance. The antibiotic does not create the mutation; it only changes which variants reproduce.

Question 36General Biology

In the lac operon of E. coli, which condition leads to maximal transcription of the structural genes?

  1. Lactose present and glucose present
  2. Lactose absent and glucose present
  3. Lactose absent and glucose absent
  4. Lactose present and glucose absent Correct answer.

Explanation

Lactose relieves repression by binding the repressor, while low glucose raises cAMP so CAP activates transcription. Maximal expression therefore requires lactose to be available and glucose to be scarce.

Question 37General Biology

A cell is treated with a drug that blocks the spindle assembly checkpoint. Which outcome is most likely if the drug takes effect?

  1. Cells arrest permanently in G1 phase before replicating DNA
  2. Cells proceed into anaphase with chromosomes that are not properly attached Correct answer.
  3. Cells replicate their DNA twice without dividing
  4. Cells complete mitosis with a normal chromosome number

Explanation

The spindle assembly checkpoint normally delays anaphase until every kinetochore is attached and tension is correct. Blocking it lets cells segregate chromosomes prematurely, producing missegregation and aneuploidy.

Question 38General Biology

A recessive allele is maintained in a large population at a low but stable frequency despite selection against homozygous affected individuals. Which force most plausibly counteracts selection in this situation?

  1. Assortative mating
  2. Directional selection favoring homozygotes
  3. Random genetic drift in a small population
  4. Mutation-selection balance Correct answer.

Explanation

New mutant alleles arise each generation and replenish the recessive allele removed by selection, producing a stable equilibrium frequency. This balance between mutation input and selective loss explains persistence of harmful recessives.

Question 39General Biology

A mutation deletes one nucleotide in the second exon of a gene, and the encoded protein is truncated and nonfunctional. Which explanation best accounts for this result?

  1. The deletion changes one codon to a chemically similar amino acid
  2. The deletion occurs in a promoter and blocks transcription initiation
  3. The deletion shifts the reading frame, creating a premature stop codon Correct answer.
  4. The deletion removes an intron, preventing splicing of the transcript

Explanation

A one-nucleotide deletion in a coding region shifts the triplet reading frame downstream, which usually produces a premature stop codon and a shortened, nonfunctional protein. The location in an exon is key, since the altered sequence is translated.

Question 40General Biology

A population of lizards on an island has a narrow snout allele that improves survival on hard-shelled prey. After a drought eliminates most soft prey, allele frequencies shift toward the narrow-snout allele over several generations. Which statement best characterizes this change?

  1. It is genetic drift caused by the founder effect
  2. It is stabilizing selection reducing phenotypic variance around the mean
  3. It is directional selection acting on heritable variation in a population Correct answer.
  4. It is gene flow from a neighboring mainland population

Explanation

The environmental change makes one extreme phenotype more advantageous, so directional selection shifts the population mean toward that trait over generations. Because the trait is heritable, allele frequencies change predictably.

Question 41General Chemistry

Which statement correctly describes the Arrhenius definition of a base in aqueous solution?

  1. A base is an electron-pair acceptor that forms a coordinate bond.
  2. A base is a proton donor that transfers H+ to water.
  3. A base is any species that increases the concentration of hydronium ions.
  4. A base is a substance that produces hydroxide ions when dissolved in water. Correct answer.

Explanation

The Arrhenius model classifies bases by the ions they release in water: a base increases the hydroxide ion concentration. This contrasts with the Bronsted-Lowry model, which defines bases as proton acceptors. The hydroxide-producing criterion is what makes Arrhenius bases distinct.

Question 42General Chemistry

A compound has a molar mass of 180 g/mol and contains 40.0% carbon by mass. How many grams of carbon are present in 0.250 mol of the compound?

  1. 18.0 g Correct answer.
  2. 4.50 g
  3. 45.0 g
  4. 72.0 g

Explanation

The mass of 0.250 mol is 0.250 times 180 g/mol, which equals 45.0 g. Carbon is 40.0% of that mass, so the carbon content is 0.400 times 45.0 g, or 18.0 g. Percent composition applies to total sample mass, not directly to the molar mass alone.

Question 43General Chemistry

Which quantum number primarily determines the shape of an atomic orbital?

  1. Spin quantum number, ms
  2. Azimuthal quantum number, l Correct answer.
  3. Magnetic quantum number, ml
  4. Principal quantum number, n

Explanation

The azimuthal (angular momentum) quantum number l defines the orbital type, s, p, d, or f, and therefore its shape. The principal quantum number sets size and energy level, while ml sets orientation. Spin describes the electron's intrinsic state, not orbital geometry.

Question 44General Chemistry

In the reaction N2(g) + 3H2(g) -> 2NH3(g), 2.0 mol of N2 reacts with 3.0 mol of H2. Which reactant limits the reaction, and how many moles of NH3 can form?

  1. N2 limits; 2.0 mol NH3 forms
  2. H2 limits; 2.0 mol NH3 forms Correct answer.
  3. N2 limits; 4.0 mol NH3 forms
  4. H2 limits; 3.0 mol NH3 forms

Explanation

The stoichiometric ratio requires 3 mol H2 per 1 mol N2, so 2.0 mol N2 would need 6.0 mol H2. Only 3.0 mol H2 is available, making H2 limiting. From 3.0 mol H2, the ratio 2 NH3 per 3 H2 gives 2.0 mol NH3.

Question 45General Chemistry

Which intermolecular force is primarily responsible for the unusually high boiling point of water compared with hydrogen sulfide?

  1. Ion-dipole interactions
  2. Hydrogen bonding Correct answer.
  3. London dispersion forces
  4. Dipole-dipole interactions

Explanation

Water forms strong hydrogen bonds because hydrogen is bonded to a highly electronegative oxygen atom with lone pairs. These bonds require significant energy to break, raising the boiling point. Hydrogen sulfide lacks hydrogen bonding because sulfur is less electronegative.

Question 46General Chemistry

A gas occupies 2.00 L at 300 K and 1.00 atm. What volume does it occupy at 600 K if the pressure is held constant?

  1. 2.00 L
  2. 1.00 L
  3. 4.00 L Correct answer.
  4. 6.00 L

Explanation

Charles's law states that volume is directly proportional to absolute temperature at constant pressure. Doubling the temperature from 300 K to 600 K doubles the volume, giving 4.00 L. Temperatures must be in kelvin for the ratio to hold.

Question 47General Chemistry

Which of the following is the correct electron configuration for a neutral iron atom (Z = 26)?

  1. [Ar] 3d8
  2. [Ar] 4s1 3d7
  3. [Ar] 4s2 4p6
  4. [Ar] 4s2 3d6 Correct answer.

Explanation

Iron has 26 electrons, and after the argon core of 18 electrons, 8 remain. These fill the 4s subshell with 2 electrons and the 3d subshell with 6, giving [Ar] 4s2 3d6. This matches the observed ground-state configuration of iron.

Question 48General Chemistry

Which factor increases the rate of a chemical reaction by lowering the activation energy?

  1. Adding a catalyst Correct answer.
  2. Decreasing the temperature
  3. Increasing the concentration of products
  4. Increasing the volume of the container

Explanation

A catalyst provides an alternative reaction pathway with a lower activation energy, increasing the fraction of collisions that succeed. It does not change the overall thermodynamics of the reaction. Other listed changes affect collision frequency or energy distribution rather than activation energy.

Question 49General Chemistry

At equilibrium, the equilibrium constant Kc for a reaction is 4.0. If the reaction quotient Q is currently 1.0, in which direction does the reaction proceed?

  1. Toward the products, because Q < K Correct answer.
  2. The system is already at equilibrium
  3. Toward the reactants, because Q < K
  4. Toward the products, because Q > K

Explanation

The reaction quotient Q is compared with K to determine the direction of net change. When Q is less than K, the forward reaction is favored and the system shifts toward products. Here Q = 1.0 is below K = 4.0, so products form.

Question 50General Chemistry

Which pair of species constitutes a conjugate acid-base pair?

  1. H2SO4 and Na2SO4
  2. NH3 and NH4+ Correct answer.
  3. CH4 and CH3OH
  4. HCl and NaOH

Explanation

A conjugate acid-base pair differs by exactly one proton. Ammonia (NH3) accepts a proton to become the ammonium ion (NH4+), so the two form a conjugate pair. The other pairs do not differ by a single H+ unit.