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Question 1Survey of the Natural Sciences - Biology

A spindle-disrupting drug prevents sister chromatids from moving toward opposite poles after metaphase. Which mitotic transition is directly blocked?

  1. The onset of interphase after cytokinesis
  2. The transition from metaphase to anaphase Correct answer.
  3. The transition from G1 to S phase
  4. The formation of a replication fork in S phase

Explanation

Anaphase begins when sister chromatids separate and move toward opposite spindle poles. Disrupting the machinery for that movement directly interferes with the metaphase-to-anaphase transition rather than DNA replication.

Question 2Survey of the Natural Sciences - Biology

A molecule that dissolves readily in water and forms hydrogen bonds with water molecules is best described as which of the following?

  1. Nonpolar
  2. Amphipathic
  3. Hydrophobic
  4. Hydrophilic Correct answer.

Explanation

Hydrophilic substances are polar or charged and interact favorably with water through hydrogen bonding or ion-dipole interactions. Hydrophobic and nonpolar substances lack this affinity, while amphipathic molecules have both polar and nonpolar regions.

Question 3Survey of the Natural Sciences - Biology

Which enzyme unwinds the DNA double helix ahead of the replication fork during DNA replication?

  1. Helicase Correct answer.
  2. DNA ligase
  3. Primase
  4. DNA polymerase III

Explanation

Helicase breaks the hydrogen bonds between complementary base pairs, separating the strands so replication can proceed. Ligase joins Okazaki fragments, polymerase synthesizes new DNA, and primase lays down RNA primers.

Question 4Survey of the Natural Sciences - 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 phenotypes?

  1. 1/16 Correct answer.
  2. 1/4
  3. 3/16
  4. 1/8

Explanation

Each gene independently shows a 1/4 chance of the recessive phenotype, so the joint probability is 1/4 x 1/4 = 1/16. Independent assortment allows multiplying the probabilities across unlinked loci.

Question 5Survey of the Natural Sciences - Biology

Which structure is the primary site of nutrient and gas exchange between maternal and fetal blood in the human placenta?

  1. Amnion
  2. Umbilical artery
  3. Myometrium
  4. Chorionic villi Correct answer.

Explanation

Chorionic villi are fingerlike projections that increase surface area and bring fetal capillaries close to maternal blood in the intervillous space, enabling exchange. The amnion is a protective membrane, and the myometrium is uterine muscle.

Question 6Survey of the Natural Sciences - Biology

Which of the following correctly describes the flow of electrons through the light-dependent reactions of photosynthesis?

  1. NADP+ to photosystem I to photosystem II
  2. Photosystem II to photosystem I to NADP+ Correct answer.
  3. Photosystem I to photosystem II to water
  4. Water to photosystem I to photosystem II

Explanation

Linear electron flow proceeds from water through photosystem II, then the cytochrome complex, then photosystem I, and finally to NADP+ via ferredoxin. This Z-scheme also generates a proton gradient for ATP synthesis.

Question 7Survey of the Natural Sciences - Biology

Which blood vessel type has the thinnest walls and is the primary site of exchange between blood and interstitial fluid?

  1. Artery
  2. Arteriole
  3. Capillary Correct answer.
  4. Vein

Explanation

Capillaries consist of a single endothelial layer, minimizing diffusion distance for gases, nutrients, and wastes. Arteries and veins have thicker, layered walls, and arterioles are resistance vessels that regulate flow into capillaries.

Question 8Survey of the Natural Sciences - Biology

Which of the following best describes the role of the enzyme that catalyzes the reaction between an amino acid and its corresponding tRNA during translation?

  1. It translocates the ribosome along the mRNA
  2. It releases the completed polypeptide from the ribosome
  3. It joins the amino acid to the tRNA by an ester bond using ATP Correct answer.
  4. It forms peptide bonds between adjacent amino acids

Explanation

Aminoacyl-tRNA synthetases use ATP to attach the correct amino acid to its tRNA, forming an aminoacyl-tRNA with an ester linkage. Peptide bond formation is catalyzed by the ribosome's peptidyl transferase activity.

Question 9Survey of the Natural Sciences - Biology

A red blood cell is placed in a hypertonic solution. Which change is expected?

  1. The cell swells and may lyse
  2. The cell shrinks as water leaves Correct answer.
  3. The cell actively pumps in water
  4. The cell remains unchanged

Explanation

In a hypertonic solution, the solute concentration outside is higher than inside, so water moves out by osmosis and the cell shrinks. Swelling occurs in hypotonic solutions, where water enters the cell.

Question 10Survey of the Natural Sciences - Biology

In humans, a male with an X-linked recessive disorder transmits the mutant allele to which of his offspring?

  1. Half of his daughters
  2. Half of his sons
  3. All of his sons
  4. All of his daughters Correct answer.

Explanation

A father passes his X chromosome to every daughter and his Y chromosome to every son, so an X-linked allele on his single X goes to all daughters. Sons receive the Y and cannot inherit the paternal X-linked allele.

Question 11Survey of the Natural Sciences - Biology

Which of the following best explains why the genetic code is described as degenerate?

  1. Several codons can specify the same amino acid Correct answer.
  2. Codons overlap so one nucleotide is used twice
  3. Each codon can specify more than one amino acid
  4. Some codons are not read during translation

Explanation

Degeneracy means that most amino acids correspond to more than one codon, largely because of wobble at the third position. It does not mean a single codon is ambiguous, and the code is read in non-overlapping triplets.

Question 12Survey of the Natural Sciences - Biology

During glycolysis, what is the net yield per molecule of glucose?

  1. 2 ATP, 4 NADH, 2 pyruvate
  2. 4 ATP, 2 NADH, 2 pyruvate
  3. 2 ATP, 2 NADH, 2 pyruvate Correct answer.
  4. 1 ATP, 1 NADH, 1 pyruvate

Explanation

Glycolysis consumes 2 ATP in the investment phase and produces 4 ATP in the payoff phase, giving a net of 2 ATP, along with 2 NADH and 2 pyruvate per glucose. The gross ATP figure of 4 is not the net yield.

Question 13Survey of the Natural Sciences - Biology

A population of organisms in Hardy-Weinberg equilibrium has a recessive allele frequency q of 0.3. What is the frequency of heterozygous individuals?

  1. 0.42 Correct answer.
  2. 0.09
  3. 0.49
  4. 0.21

Explanation

Heterozygote frequency equals 2pq, with p = 1 - 0.3 = 0.7, giving 2(0.7)(0.3) = 0.42. The value q squared, 0.09, is the homozygous recessive frequency, not the heterozygote frequency.

Question 14Survey of the Natural Sciences - Biology

Which of the following is a distinguishing feature of members of the kingdom Fungi compared with members of the kingdom Plantae?

  1. Fungi reproduce only by binary fission
  2. Fungi perform photosynthesis using chlorophyll
  3. Fungi are always unicellular
  4. Fungi possess cell walls made of chitin Correct answer.

Explanation

Fungal cell walls are composed primarily of chitin, whereas plant cell walls contain cellulose. Fungi are heterotrophic, so they do not photosynthesize, and most are multicellular with diverse reproductive modes.

Question 15Survey of the Natural Sciences - Biology

Which of the following correctly pairs a hormone with its principal action in the human body?

  1. Calcitonin - raises blood calcium
  2. Insulin - raises blood glucose
  3. Glucagon - lowers blood glucose
  4. Aldosterone - promotes sodium reabsorption Correct answer.

Explanation

Aldosterone, a mineralocorticoid from the adrenal cortex, increases sodium reabsorption and potassium secretion in the kidney. Insulin lowers glucose, glucagon raises it, and calcitonin lowers blood calcium.

Question 16Survey of the Natural Sciences - Biology

A mutation changes a single nucleotide in a coding region but the amino acid sequence of the protein remains unchanged. This is best described as which type of mutation?

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

Explanation

A silent mutation alters a codon but, due to degeneracy of the genetic code, specifies the same amino acid. Missense changes the amino acid, nonsense creates a stop codon, and frameshift shifts the reading frame.

Question 17Survey of the Natural Sciences - Biology

In which organelle are the enzymes of the Krebs cycle primarily located in eukaryotic cells?

  1. Rough endoplasmic reticulum
  2. Mitochondrial matrix Correct answer.
  3. Golgi apparatus
  4. Cytosol

Explanation

Most Krebs cycle enzymes are soluble in the mitochondrial matrix, except succinate dehydrogenase, which is bound to the inner membrane. Glycolysis, by contrast, occurs in the cytosol.

Question 18Survey of the Natural Sciences - Biology

A researcher observes that a particular species of flowering plant produces flowers only when the nights exceed a critical length. This plant is best classified as which of the following?

  1. Day-neutral plant
  2. Long-day plant
  3. Facultative halophyte
  4. Short-day plant Correct answer.

Explanation

Short-day plants flower when the dark period exceeds a critical length, so long nights promote flowering. Long-day plants flower when nights are shorter than a critical length, and day-neutral plants are insensitive to photoperiod.

Question 19Survey of the Natural Sciences - Biology

Which of the following best explains the role of the sodium-potassium pump in maintaining the resting membrane potential of a neuron?

  1. It moves three sodium ions out and two potassium ions in, contributing to a negative interior Correct answer.
  2. It generates action potentials directly by opening voltage-gated channels
  3. It allows sodium and potassium to diffuse freely across the membrane
  4. It moves two sodium ions out and three potassium ions in, contributing to a positive interior

Explanation

The pump uses ATP to export three Na+ and import two K+, leaving a net deficit of positive charge inside and contributing a small electrogenic effect. The resulting gradients are then used by channels during signaling.

Question 20Survey of the Natural Sciences - Biology

Which of the following correctly describes the relationship between the Calvin cycle and the light reactions of photosynthesis?

  1. The Calvin cycle produces oxygen as a byproduct
  2. The Calvin cycle supplies ATP and NADPH to the light reactions
  3. The light reactions supply ATP and NADPH to the Calvin cycle, which fixes carbon dioxide Correct answer.
  4. The light reactions fix carbon dioxide directly

Explanation

The light reactions generate ATP and NADPH, which the Calvin cycle uses to reduce carbon dioxide into sugar. Oxygen is released by the light reactions during water splitting, not by the Calvin cycle.

Question 21Survey of the Natural Sciences - Biology

In a pedigree, a trait appears in every generation, affects approximately half of the offspring of an affected parent regardless of sex, and does not skip generations. This pattern is most consistent with which mode of inheritance?

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

Explanation

Autosomal dominant traits typically appear in every generation, affect males and females similarly, and give roughly a 50 percent chance of transmission from a heterozygous affected parent. Recessive traits often skip generations, and mitochondrial traits pass through mothers.

Question 22Survey of the Natural Sciences - Biology

A cell with a mutation that prevents formation of the synaptonemal complex would most directly impair which process?

  1. Attachment of amino acids to tRNA
  2. Separation of sister chromatids in mitosis
  3. Pairing of homologous chromosomes during meiosis Correct answer.
  4. Formation of the mitotic spindle

Explanation

The synaptonemal complex is a protein scaffold that holds homologous chromosomes together during prophase I, enabling crossing over. Without it, homolog pairing and recombination are disrupted.

Question 23Survey of the Natural Sciences - Biology

A competitive inhibitor is added to an enzyme-catalyzed reaction. Which kinetic change is expected?

  1. The maximum velocity decreases while the Michaelis constant is unchanged
  2. The apparent Michaelis constant increases while maximum velocity is unchanged Correct answer.
  3. The maximum velocity increases without changing the Michaelis constant
  4. Both the maximum velocity and the Michaelis constant decrease

Explanation

A competitive inhibitor binds the active site reversibly, raising the apparent Km because more substrate is needed to compete, but high substrate can still reach the same Vmax. Noncompetitive inhibitors instead reduce Vmax.

Question 24Survey of the Natural Sciences - Biology

A population of insects colonizes a new island with a small founding group, and after many generations the population shows reduced genetic variation compared with the mainland source. Which evolutionary mechanism best explains this outcome?

  1. Natural selection
  2. Directional selection
  3. Gene flow
  4. Founder effect Correct answer.

Explanation

The founder effect is a form of genetic drift in which a small colonizing group carries only a subset of the source population's alleles, reducing variation. Selection and gene flow would not by themselves produce the reduction seen with a small founding group.

Question 25Survey of the Natural Sciences - Biology

A plant is grown in soil lacking nitrogen-fixing bacteria, and its leaves become pale and stunted. Which explanation best accounts for this observation?

  1. Phosphorus deficiency blocks ATP synthesis entirely
  2. Potassium deficiency prevents water uptake by roots
  3. Magnesium excess causes chlorophyll degradation
  4. Nitrogen deficiency limits synthesis of amino acids and chlorophyll Correct answer.

Explanation

Nitrogen is a key component of amino acids, proteins, and chlorophyll, so deficiency leads to chlorosis and poor growth. The scenario specifies a lack of nitrogen-fixing bacteria, which limits available nitrogen.

Question 26Survey of the Natural Sciences - Biology

Which structure directly connects the cytoplasm of two adjacent plant cells and permits the passage of ions and small molecules between them?

  1. Tight junction
  2. Plasmodesma Correct answer.
  3. Desmosome
  4. Gap junction

Explanation

Plasmodesmata are channels that traverse the plant cell wall and link the cytoplasm of neighboring cells, forming the symplast. They allow ions, metabolites, and small signaling molecules to move directly between cells. The other junction types occur in animal tissues.

Question 27Survey of the Natural Sciences - Biology

A human somatic cell in G2 phase contains how many chromatids, given that the diploid chromosome number is 46?

  1. 92 Correct answer.
  2. 46
  3. 184
  4. 23

Explanation

After S phase, each of the 46 chromosomes has been replicated into two sister chromatids, so the G2 cell contains 92 chromatids. The chromosome number remains 46 because the sisters are still joined at the centromere. Chromatid number doubles only transiently during replication, not chromosome number.

Question 28Survey of the Natural Sciences - Biology

Which statement correctly describes the role of the operon's repressor protein in the lac operon when lactose is absent?

  1. It acts as a coactivator that recruits RNA polymerase to the cap site
  2. It binds the operator and blocks RNA polymerase from transcribing the structural genes Correct answer.
  3. It cleaves lactose into glucose and galactose within the cytoplasm
  4. It binds the promoter and enhances transcription of the structural genes

Explanation

In the absence of lactose, the LacI repressor remains bound to the operator sequence, physically preventing RNA polymerase from advancing into the structural genes. When lactose is present, allolactose binds the repressor and reduces its affinity for the operator, allowing transcription.

Question 29Survey of the Natural Sciences - Biology

Which tissue type lines the alveoli of the lungs, where its thinness minimizes the diffusion distance for gases?

  1. Pseudostratified ciliated columnar epithelium
  2. Simple squamous epithelium Correct answer.
  3. Stratified squamous epithelium
  4. Simple cuboidal epithelium

Explanation

Simple squamous epithelium consists of a single flat layer of cells, giving the alveolar wall a minimal thickness that favors rapid gas diffusion. Stratified and columnar epithelia are thicker or adapted for protection and secretion. Simple cuboidal epithelium is typical of tubules and ducts, not gas-exchange surfaces.

Question 30Survey of the Natural Sciences - Biology

A woman who is a carrier of an X-linked recessive allele and a man who is unaffected have a daughter. What is the probability that the daughter is a carrier?

  1. 0
  2. 1/2 Correct answer.
  3. 3/4
  4. 1/4

Explanation

The father contributes his normal X to every daughter, so daughters are never affected. Each daughter independently inherits either the mother's mutant X or her normal X with equal probability, giving a 1/2 chance of being a carrier. The sex of the child is already specified, so no additional factor of 1/2 is applied.

Question 31Survey of the Natural Sciences - Biology

In a cross between two heterozygous individuals for a single gene showing complete dominance, what phenotypic ratio is expected among the offspring?

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

Explanation

A monohybrid cross between two heterozygotes yields genotypes in a 1:2:1 ratio, but because the heterozygote and homozygous dominant share the same phenotype under complete dominance, the phenotypic ratio collapses to 3:1. The 1:2:1 ratio describes genotypes, not phenotypes, in this case.

Question 32Survey of the Natural Sciences - Biology

Which feature of the mammalian small intestine most directly increases the surface area available for nutrient absorption?

  1. Abundance of goblet cells producing mucus
  2. Presence of villi and microvilli on the mucosal surface Correct answer.
  3. Secretion of hydrochloric acid into the lumen
  4. Presence of a thick layer of smooth muscle in the wall

Explanation

Villi are fingerlike projections of the mucosa, and microvilli are apical membrane folds on the absorptive cells. Together they multiply the luminal surface area many times over, enhancing absorption. The other features serve motility, protection, or secretion rather than surface-area amplification.

Question 33Survey of the Natural Sciences - Biology

During the light-independent reactions, what is the immediate consequence of a shortage of NADPH in the chloroplast stroma?

  1. Regeneration of ribulose-1,5-bisphosphate is accelerated
  2. Proton pumping across the thylakoid membrane increases
  3. Reduction of 1,3-bisphosphoglycerate to glyceraldehyde-3-phosphate is impaired Correct answer.
  4. Fixation of carbon dioxide by rubisco is directly blocked at the active site

Explanation

NADPH supplies the reducing power for the reduction phase of the Calvin cycle, converting 1,3-bisphosphoglycerate into glyceraldehyde-3-phosphate. Without sufficient NADPH, this step slows and the cycle's output declines. Carbon fixation itself consumes ATP and carbon dioxide, not NADPH directly.

Question 34Survey of the Natural Sciences - Biology

A cell is placed in a solution and immediately begins to lose water and shrivel. Which property of the solution best explains this observation?

  1. It contains no solutes at all
  2. It has a higher solute concentration than the cytoplasm Correct answer.
  3. It has a lower solute concentration than the cytoplasm
  4. It has the same solute concentration as the cytoplasm

Explanation

Water moves by osmosis from a region of higher water potential to one of lower water potential. A solution with a higher solute concentration than the cytoplasm is hypertonic, so water exits the cell and it shrinks. An isotonic solution would produce no net change, and a hypotonic one would cause swelling.

Question 35Survey of the Natural Sciences - Biology

Which statement best distinguishes the role of the rough endoplasmic reticulum from that of the smooth endoplasmic reticulum?

  1. The rough ER synthesizes lipids, whereas the smooth ER modifies proteins destined for secretion
  2. The rough ER packages proteins into vesicles, whereas the smooth ER degrades worn-out organelles
  3. The rough ER synthesizes and folds proteins for secretion, whereas the smooth ER synthesizes lipids and detoxifies compounds Correct answer.
  4. The rough ER generates ATP, whereas the smooth ER stores genetic material

Explanation

Ribosomes studding the rough ER synthesize proteins that are translocated into the lumen, where folding and initial glycosylation occur before transport. The smooth ER lacks bound ribosomes and specializes in lipid and steroid synthesis, detoxification, and calcium storage. Vesicle packaging is chiefly a Golgi function.

Question 36Survey of the Natural Sciences - Biology

A molecule moves across a plasma membrane down its concentration gradient through a protein channel without expenditure of ATP. This transport is best classified as which of the following?

  1. Simple diffusion
  2. Primary active transport
  3. Endocytosis
  4. Facilitated diffusion Correct answer.

Explanation

Facilitated diffusion uses membrane proteins to move solutes down their concentration gradient without energy input. Simple diffusion would not require a protein, and active transport would move solutes against the gradient using ATP. Endocytosis is a bulk uptake process involving membrane invagination.

Question 37Survey of the Natural Sciences - Biology

Which process produces genetic variation in offspring by exchanging reciprocal segments between homologous chromosomes?

  1. Crossing over during prophase I Correct answer.
  2. Fertilization of two haploid gametes
  3. Separation of sister chromatids during anaphase II
  4. Independent assortment during metaphase I

Explanation

Crossing over occurs during prophase I, when homologous chromosomes pair as tetrads and reciprocal segments are exchanged at chiasmata. This recombination creates new combinations of alleles on a single chromosome. Independent assortment and fertilization also generate variation but do not involve exchange of chromosome segments.

Question 38Survey of the Natural Sciences - Biology

A cell is treated with a drug that blocks the activity of the enzyme responsible for adding poly(A) tails to mRNA. Which consequence is most likely?

  1. Transcription initiation by RNA polymerase II would be prevented
  2. Introns would fail to be removed from the primary transcript
  3. The mRNA would be translated without a start codon
  4. The mRNA would be less stable and more susceptible to degradation Correct answer.

Explanation

The poly(A) tail protects the 3' end of eukaryotic mRNA from exonuclease degradation and contributes to export and translation efficiency. Blocking polyadenylation therefore reduces stability and shortens the mRNA's functional lifetime. Splicing, initiation, and start codon selection depend on other machinery.

Question 39Survey of the Natural Sciences - Biology

A population of rabbits is introduced to an island with abundant food and no predators. Which pattern of growth is expected initially, and what limits it over time?

  1. Linear growth, limited by a constant birth rate
  2. Logistic growth, limited only by mutation rate
  3. Exponential growth that continues indefinitely without limit
  4. Logistic growth, limited by environmental carrying capacity as resources decline Correct answer.

Explanation

With abundant resources and little resistance, the population initially grows rapidly, approximating exponential growth. As density rises, competition for food and space increases, slowing growth until the population levels off at the carrying capacity, producing an S-shaped logistic curve.

Question 40Survey of the Natural Sciences - Biology

Two enzymes catalyze the same reaction but have different Michaelis constants. Which statement correctly compares them when substrate concentration is well below the Michaelis constant?

  1. The enzyme with the lower Michaelis constant has a lower maximum velocity by definition
  2. The enzyme with the lower Michaelis constant reaches a higher fraction of its maximum velocity at that substrate concentration Correct answer.
  3. Both enzymes operate at maximum velocity regardless of substrate concentration
  4. The enzyme with the higher Michaelis constant has greater affinity for the substrate

Explanation

The Michaelis constant equals the substrate concentration at which velocity is half maximal, so a lower value indicates higher substrate affinity. At substrate concentrations well below the constant, the enzyme with the lower value is closer to saturation and achieves a larger fraction of its maximum velocity. Maximum velocity itself is not determined by the constant.

Question 41Survey of the Natural Sciences - General Chemistry

Which statement correctly describes the trend in first ionization energy across Period 3 from sodium to argon?

  1. It decreases steadily because added electrons shield one another strongly.
  2. It increases only for noble gases and decreases for all metals.
  3. It remains essentially constant because all these elements fill the 3s and 3p subshells.
  4. It increases overall because effective nuclear charge rises while electrons are added to the same shell. Correct answer.

Explanation

Across a period, protons are added to the nucleus while new electrons enter the same principal shell, so effective nuclear charge rises and the outer electron is held more tightly. Small dips occur at group 13 and group 16 due to subshell and pairing effects, but the overall trend is upward.

Question 42Survey of the Natural Sciences - General Chemistry

A sample of an ideal gas occupies 2.0 L at 300 K and 1.0 atm. If the pressure is doubled while the temperature is held constant, what volume does the gas occupy?

  1. 4.0 L
  2. 1.0 L Correct answer.
  3. 0.5 L
  4. 2.0 L

Explanation

Boyle's law states that at constant temperature, pressure and volume are inversely proportional (P1V1 = P2V2). Doubling the pressure from 1.0 atm to 2.0 atm halves the volume from 2.0 L to 1.0 L.

Question 43Survey of the Natural Sciences - General Chemistry

Which of the following is the correct electron configuration for a neutral chlorine atom (Z = 17)?

  1. 1s² 2s² 2p⁵ 3s² 3p⁶
  2. 1s² 2s² 2p⁶ 3s² 3p⁵ Correct answer.
  3. 1s² 2s² 2p⁶ 3s² 3p⁶
  4. 1s² 2s² 2p⁶ 3s² 3p⁴ 4s¹

Explanation

Chlorine has 17 electrons, which fill orbitals in order of increasing energy: 1s (2), 2s (2), 2p (6), 3s (2), and 3p (5), totaling 17. The configuration 1s² 2s² 2p⁶ 3s² 3p⁵ satisfies both the Aufbau principle and Hund's rule.

Question 44Survey of the Natural Sciences - General Chemistry

What is the molar mass of calcium carbonate, CaCO₃? (Ca = 40.1, C = 12.0, O = 16.0 g/mol)

  1. 68.1 g/mol
  2. 100.1 g/mol Correct answer.
  3. 116.1 g/mol
  4. 84.1 g/mol

Explanation

The molar mass is the sum of atomic masses: 40.1 (Ca) + 12.0 (C) + 3 × 16.0 (O) = 40.1 + 12.0 + 48.0 = 100.1 g/mol. Each of the three oxygen atoms must be counted.

Question 45Survey of the Natural Sciences - General Chemistry

Which type of intermolecular force is primarily responsible for the relatively high boiling point of water compared with hydrogen sulfide, H₂S?

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

Explanation

Water molecules form extensive hydrogen bonds because hydrogen is bonded to the highly electronegative oxygen atom, giving each molecule two donors and two acceptors. These strong interactions require more energy to overcome, raising the boiling point well above that of H₂S, which lacks effective hydrogen bonding.

Question 46Survey of the Natural Sciences - General Chemistry

In the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g), which change would shift the equilibrium toward the products at constant temperature?

  1. Removing some hydrogen gas
  2. Increasing the volume of the container
  3. Increasing the partial pressure of nitrogen Correct answer.
  4. Adding a catalyst

Explanation

By Le Châtelier's principle, raising the partial pressure of a reactant drives the equilibrium toward products. Increasing nitrogen concentration makes the forward reaction rate temporarily greater, consuming N₂ and H₂ to form more NH₃.

Question 47Survey of the Natural Sciences - General Chemistry

Which of the following solutions would have a pH greater than 7 at 25 °C?

  1. 0.10 M CH₃COOH
  2. 0.10 M NaOH Correct answer.
  3. 0.10 M NaCl
  4. 0.10 M HCl

Explanation

Sodium hydroxide is a strong base that dissociates completely, giving a hydroxide concentration of 0.10 M and a pH near 13, well above 7. A pH above 7 at 25 °C indicates a basic solution.

Question 48Survey of the Natural Sciences - General Chemistry

Which quantum number determines the overall shape of an atomic orbital (s, p, d, or f)?

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

Explanation

The angular momentum quantum number ℓ takes values from 0 to n−1 and defines the orbital type: ℓ = 0 is s, 1 is p, 2 is d, and 3 is f. The principal quantum number sets the shell and size, while mℓ and ms describe orientation and spin.

Question 49Survey of the Natural Sciences - General Chemistry

How many moles of oxygen gas are required to completely combust 2.0 moles of methane, CH₄, according to the balanced equation CH₄ + 2O₂ → CO₂ + 2H₂O?

  1. 3.0 mol
  2. 1.0 mol
  3. 4.0 mol Correct answer.
  4. 2.0 mol

Explanation

The balanced equation shows a 1:2 mole ratio between methane and oxygen, so 2.0 moles of CH₄ require 2 × 2.0 = 4.0 moles of O₂. The coefficients give the stoichiometric ratio directly.

Question 50Survey of the Natural Sciences - General Chemistry

A 25.0 mL sample of 0.100 M HCl is titrated with 0.100 M NaOH. What is the pH at the equivalence point?

  1. pH = 7.0 Correct answer.
  2. pH = 1.0
  3. pH = 13.0
  4. pH = 4.7

Explanation

At the equivalence point, all HCl has been neutralized by NaOH to form NaCl and water. Because both are strong, the resulting solution is neutral and the pH is 7.0 at 25 °C.