ADVANCED GENERAL CHEMISTRY II -
CHEM134 C003 QUESTIONS AND
ANSWERS WITH VERIFIED SOLUTIONS
2026/2027 UPDATE. JUST RELEASED
1. Calculate the pH of a 0.15 M solution of ammonium chloride (NH4Cl), given that the Kb for
ammonia (NH3) is 1.8 x 10^-5.
A. 4.74
B. 8.96
C. 5.04
D. 5.27
Answer: C
Conceptual Explanation: NH4+ is the conjugate acid of a weak base. Ka = Kw/Kb = 1.0e-
.8e-5 = 5.56e-10. [H+] = sqrt(Ka * C) = sqrt(5.56e-10 * 0.15) = 9.13e-6. pH = -
log(9.13e-6) = 5.04.
,2. Which of the following mixtures would result in a buffer solution with the highest capacity
against both acid and base?
A. 0.1 M CH3COOH and 0.1 M NaCH3COO
B. 0.5 M CH3COOH and 0.5 M NaCH3COO
C. 0.5 M CH3COOH and 0.1 M NaCH3COO
D. 0.1 M HCl and 0.1 M NaCl
Answer: B
Conceptual Explanation: Buffer capacity increases with higher concentrations of both the
weak acid and its conjugate base. 0.5 M concentrations provide more moles to neutralize
added H+ or OH- compared to 0.1 M.
3. For the reaction N2(g) + 3H2(g) -> 2NH3(g), what is the sign of the standard entropy change
(ΔS°)?
A. Positive
B. Negative
C. Zero
D. Cannot be determined
Answer: B
, Conceptual Explanation: The reaction involves a decrease in the number of moles of gas
(from 4 moles of reactants to 2 moles of products), which leads to a decrease in molecular
disorder and thus a negative ΔS°.
4. Calculate the molar solubility of Ag2CrO4 in water if its Ksp is 1.1 x 10^-12.
A. 1.0 x 10^-4 M
B. 8.2 x 10^-5 M
C. 1.3 x 10^-4 M
D. 6.5 x 10^-5 M
Answer: D
Conceptual Explanation: Ksp = [Ag+]^2 [CrO4^2-]. If solubility is s, then [Ag+]=2s and
[CrO4^2-]=s. Ksp = (2s)^2 * s = 4s^3. s = (Ksp/4)^(1/3) = (1.1e-)^(1/3) = 6.5e-5 M.
5. Under what conditions is a reaction always spontaneous?
A. ΔH > 0 and ΔS > 0
B. ΔH < 0 and ΔS > 0
C. ΔH < 0 and ΔS < 0
D. ΔH > 0 and ΔS < 0
Answer: B
CHEM134 C003 QUESTIONS AND
ANSWERS WITH VERIFIED SOLUTIONS
2026/2027 UPDATE. JUST RELEASED
1. Calculate the pH of a 0.15 M solution of ammonium chloride (NH4Cl), given that the Kb for
ammonia (NH3) is 1.8 x 10^-5.
A. 4.74
B. 8.96
C. 5.04
D. 5.27
Answer: C
Conceptual Explanation: NH4+ is the conjugate acid of a weak base. Ka = Kw/Kb = 1.0e-
.8e-5 = 5.56e-10. [H+] = sqrt(Ka * C) = sqrt(5.56e-10 * 0.15) = 9.13e-6. pH = -
log(9.13e-6) = 5.04.
,2. Which of the following mixtures would result in a buffer solution with the highest capacity
against both acid and base?
A. 0.1 M CH3COOH and 0.1 M NaCH3COO
B. 0.5 M CH3COOH and 0.5 M NaCH3COO
C. 0.5 M CH3COOH and 0.1 M NaCH3COO
D. 0.1 M HCl and 0.1 M NaCl
Answer: B
Conceptual Explanation: Buffer capacity increases with higher concentrations of both the
weak acid and its conjugate base. 0.5 M concentrations provide more moles to neutralize
added H+ or OH- compared to 0.1 M.
3. For the reaction N2(g) + 3H2(g) -> 2NH3(g), what is the sign of the standard entropy change
(ΔS°)?
A. Positive
B. Negative
C. Zero
D. Cannot be determined
Answer: B
, Conceptual Explanation: The reaction involves a decrease in the number of moles of gas
(from 4 moles of reactants to 2 moles of products), which leads to a decrease in molecular
disorder and thus a negative ΔS°.
4. Calculate the molar solubility of Ag2CrO4 in water if its Ksp is 1.1 x 10^-12.
A. 1.0 x 10^-4 M
B. 8.2 x 10^-5 M
C. 1.3 x 10^-4 M
D. 6.5 x 10^-5 M
Answer: D
Conceptual Explanation: Ksp = [Ag+]^2 [CrO4^2-]. If solubility is s, then [Ag+]=2s and
[CrO4^2-]=s. Ksp = (2s)^2 * s = 4s^3. s = (Ksp/4)^(1/3) = (1.1e-)^(1/3) = 6.5e-5 M.
5. Under what conditions is a reaction always spontaneous?
A. ΔH > 0 and ΔS > 0
B. ΔH < 0 and ΔS > 0
C. ΔH < 0 and ΔS < 0
D. ΔH > 0 and ΔS < 0
Answer: B
