Admission Tests Admission Tests Certifications PCAT Questions & Answers

• Question 181:

  An enzyme reaction reaches _____ at _____.

  A. Vmax, Km

  B. Vmax, 1/2 Km

  C. 1/2 Vmax, Km

  D. 1/2 Vmax, 1/2 Km

  Correct Answer: C

  Vmax is the maximum rate at which an enzymatic reaction can occur. Km is the substrate concentration yielding a reaction rate that is half of the maximum reaction rate.

• Question 182:

  What is the molecular formula of acetic acid?

  A. C2H4O2

  B. C3H6O

  C. CH2O

  D. CHO

  Correct Answer: A

• Question 183:

  What effect would doubling the volume and temperature of an ideal gas have on its pressure?

  A. double the pressure

  B. half the pressure

  C. make the pressure zero

  D. no effect

  Correct Answer: D

  The ideal gas law states: pV = NRT, where p is pressure, V is volume, N is the amount, R is the ideal gas constant, and T is the gas's temperature. Doubling the volume, V = 2V, and doubling the temperature, T = 2T, will have not alter the pressure because the 2's on both sides of the equation will cancel, yielding the original pressure.

• Question 184:

  ______ law states that the ______ is the sum of ______ in a gas compound.

  A. Dalton's, partial pressure, total pressure

  B. Henry's, partial pressure, total pressure

  C. Dalton's, total pressure, partial pressures

  D. Henry's, total pressure, partial pressures

  Correct Answer: C

  Dalton's law states that the total pressure of a gaseous compound is the sum of the partial pressures of each gas making up the compound:

  

• Question 185:

  Which would yield an endothermic reaction?

  A. ∆G = 298 T = 298

  ∆S = −1

  B. ∆G = −298 T = 298 ∆S= −2

  C. ∆G = −298 T = 0 ∆S = 1

  D. none of them

  Correct Answer: D

  The free energy change of a reaction, ∆G, is equal to the difference between ∆H, the change in enthalpy, and the product of the temperature, T, with the change in entropy, ∆S, of the system: ∆G = ∆H − T∆S. An endothermic reaction requires a ∆H > 0. Solve for ∆H in each case. (A): 0, (B): −894, (C): −298.

• Question 186:

  In which locations does this reaction occur?

  Glyceraldehyde-3-phosphate (G3P) –––––andgt; Pyruvate

  A. cytoplasm

  B. nucleus

  C. mitochondria

  D. none of the above

  Correct Answer: A

  The oxidation of G3P into pyruvate occurs during the glycolysis stage of cellular respiration. Glycolysis occurs in the cytoplasm.

• Question 187:

  The addition of HBr with peroxide and an alkene yields what product?

  A. Markovnikov's product

  B. anti-Markovnikov's product

  C. Saytzeff's product

  D. the ortho product

  Correct Answer: B

  In the absence of peroxide, HBr plus an alkene yields Markovnikov's product. But, in the presence of peroxide, the result of the reaction is an anti-Markovnikov's product.

• Question 188:

  Which of the following would have the highest pH in a solution?

  A. hydrofluoric acid

  B. water

  C. ammonia

  D. hydrochloric acid

  Correct Answer: C

  Because ammonia can accept protons from water molecules, it is considered basic. Water is considered neutral, and both hydrofluoric and hydrochloric acid have low pH's because they ionize in aqueous solutions. Ammonia, a base, has the highest pH of the answer choices.

• Question 189:

  The distribution of electrons evenly in a molecule contributes to stability. This accounts for:

  A. atomic mass

  B. valence

  C. resonance

  D. electronegativity

  Correct Answer: C

  Resonance describes the possible positions of electrons within a molecule when more than one possibility exists. Molecules that have multiple resonance structures display greater stability than those with fewer resonance structures.

• Question 190:

  Rank the following compounds based on increasing acidity:

  I. CH3CH2OH

  II. CH3COCH3

  III. CH3CH2COH

  IV.

  CH3CH2COOH

  A.

  II, III, IV, I

  B.

  II, IV, I, III

  C.

  II, III, I, IV

  D.

  IV, I, III, II

  Correct Answer: C