CHEM 210 Biochemistry: Water, pH, and Buffers Exam 2026/2027
UPDATE
1. Which of the following best describes the geometry of a single water
molecule?
A. Linear
B. Bent
C. Trigonal planar
D. Octahedral
Answer: B
Rationale: Water has a bent geometry with a bond angle of approximately 104.5 degrees
due to the two lone pairs on the oxygen atom.
2. What type of bond forms between the oxygen atom of one water molecule
and the hydrogen atom of another?
A. Hydrogen bond
B. Covalent bond
C. Ionic bond
D. Van der Waals force
Answer: A
Rationale: Hydrogen bonds occur between the partial positive charge of a hydrogen atom
and the partial negative charge of an electronegative atom like oxygen in a neighboring
molecule.
,3. Which property of water allows it to resist drastic changes in temperature?
A. Adhesion
B. Low density as a solid
C. High surface tension
D. High heat capacity
Answer: D
Rationale: Water’s high specific heat capacity means it can absorb or lose a significant
amount of heat with minimal change in temperature.
4. In a water molecule, the oxygen atom is more ____ than the hydrogen atoms.
A. Electropositive
B. Nonpolar
C. Hydrophobic
D. Electronegative
Answer: D
Rationale: Oxygen is highly electronegative, meaning it attracts electrons more strongly
than hydrogen, leading to a dipole.
5. The ion product of water (Kw) at 25°C is equal to:
A. 1.0 x 10^-7
B. 1.0 x 10^-14
C. 7.0
D. 1.0 x 10^14
Answer: B
Rationale: Kw = [H+][OH-] = 1.0 x 10^-14 at 25 degrees Celsius.
, 6. If the pH of a solution is 4, what is the concentration of [H+] ions?
A. 10^4 M
B. 10^-4 M
C. 4 M
D. 10^-10 M
Answer: B
Rationale: pH is defined as -log[H+]. Therefore, [H+] = 10^-pH, which is 10^-4 M.
7. A solution with a pH of 9 is considered:
A. Neutral
B. Basic
C. Acidic
D. Insoluble
Answer: B
Rationale: A pH greater than 7 is basic (alkaline), while a pH less than 7 is acidic.
8. Which equation relates pH, pKa, and the ratio of conjugate base to weak
acid?
A. Gibbs Free Energy Equation
B. Michaelis-Menten Equation
C. Henderson-Hasselbalch Equation
D. Nernst Equation
Answer: C
Rationale: The Henderson-Hasselbalch equation is pH = pKa + log([A-]/[HA]).
UPDATE
1. Which of the following best describes the geometry of a single water
molecule?
A. Linear
B. Bent
C. Trigonal planar
D. Octahedral
Answer: B
Rationale: Water has a bent geometry with a bond angle of approximately 104.5 degrees
due to the two lone pairs on the oxygen atom.
2. What type of bond forms between the oxygen atom of one water molecule
and the hydrogen atom of another?
A. Hydrogen bond
B. Covalent bond
C. Ionic bond
D. Van der Waals force
Answer: A
Rationale: Hydrogen bonds occur between the partial positive charge of a hydrogen atom
and the partial negative charge of an electronegative atom like oxygen in a neighboring
molecule.
,3. Which property of water allows it to resist drastic changes in temperature?
A. Adhesion
B. Low density as a solid
C. High surface tension
D. High heat capacity
Answer: D
Rationale: Water’s high specific heat capacity means it can absorb or lose a significant
amount of heat with minimal change in temperature.
4. In a water molecule, the oxygen atom is more ____ than the hydrogen atoms.
A. Electropositive
B. Nonpolar
C. Hydrophobic
D. Electronegative
Answer: D
Rationale: Oxygen is highly electronegative, meaning it attracts electrons more strongly
than hydrogen, leading to a dipole.
5. The ion product of water (Kw) at 25°C is equal to:
A. 1.0 x 10^-7
B. 1.0 x 10^-14
C. 7.0
D. 1.0 x 10^14
Answer: B
Rationale: Kw = [H+][OH-] = 1.0 x 10^-14 at 25 degrees Celsius.
, 6. If the pH of a solution is 4, what is the concentration of [H+] ions?
A. 10^4 M
B. 10^-4 M
C. 4 M
D. 10^-10 M
Answer: B
Rationale: pH is defined as -log[H+]. Therefore, [H+] = 10^-pH, which is 10^-4 M.
7. A solution with a pH of 9 is considered:
A. Neutral
B. Basic
C. Acidic
D. Insoluble
Answer: B
Rationale: A pH greater than 7 is basic (alkaline), while a pH less than 7 is acidic.
8. Which equation relates pH, pKa, and the ratio of conjugate base to weak
acid?
A. Gibbs Free Energy Equation
B. Michaelis-Menten Equation
C. Henderson-Hasselbalch Equation
D. Nernst Equation
Answer: C
Rationale: The Henderson-Hasselbalch equation is pH = pKa + log([A-]/[HA]).
