CHEM 111B PRACTICE EXAM 4 QUESTIONS WITH VERIFIED SOLUTIONS LATEST UPDATE 2026
Of the following, the entropy of which molecule would be the largest?
a) HCl (l)
b) HCl (g)
c) HBr (g)
d) HI (g) - Answers d
Ksp = 2.0 x 10-31 at 298 K for Al(OH)3(s).
What is the ΔG° at this temperature for the precipitation of Al(OH)3, according to the stoichiometric
equation: Al3+(aq) + 3OH-(aq) → Al(OH)3(s)? - Answers -175 kJ/mol
The Boltzmann formula is S = k ln W. A perfect crystal has a molar entropy of zero at absolute zero
because.... - Answers W=1
For a reaction, it was found that ΔH° = -140 kJ mol-1, and ΔSo = 120 J K-1 mol-1. This reaction would
be.... - Answers Spontaneous at all temperatures
Aluminum forms a layer of aluminum oxide when exposed to air, which protects the bulk metal from
further corrosion.
4Al(s) + 3O2(g) → 2Al2O3(s)
Calculate ΔG° for this reaction, given that ΔG°f of aluminum oxide is -1576.4 kJ/mol. - Answers -
3152.8 kJ/mol
What is the coefficient of iodide when the following equation is balanced in acidic solution? MnO4-
(aq) + I-(aq) → Mn2+(aq) + I2(aq) - Answers 10
Doubling all the coefficients in the equation for a cell reaction... - Answers doubles ΔG°, but does not
change E°
The standard voltage for a cell using the overall cell reaction
2Al(s) + 3I2(s) → 2Al3+(aq) + 6I-(aq) is +2.20V.
The cell voltage generated when [Al3+] = 0.150 M and [I-] = 4.5 x 10-3 M is... - Answers 2.35 V
The reaction rates of many spontaneous reactions are actually very slow. Which of these statements
is the best explanation for this observation?
a) Kp for the reaction is less than one.
b) ΔG° for the reaction is positive
c) the activation energy of the reaction is large
d) the entropy change is negative - Answers c
Complete and balance the following redox equation occurring in an acidic solution using the smallest
whole-number coefficients.
Sn + HNO3 ® SnO2 + NO2 + H2O
What is the coefficient of Sn in the balanced equation? - Answers 1
Given the information that:
2SO3 (g) ® 2S (s) + 3O2 (g)
ΔH° = 791.4 kJ
ΔG° = 742.2 kJ
Based on these values, calculate DHf° (kJ mol-1) for SO3? - Answers -395.7
Determine the change in entropy that occurs in the boiling of 18 g of water at 100 °C at ambient
pressure, ΔHvap = 40.7 kJ/mol - Answers -109 J/K
ΔG°f of water is - 237 kJ/mol. Determine if the water decomposition reaction, 2H2O(l) ⇌ O2 (g) +
H2(g) is exothermic or endothermic? - Answers Endothermic
Determine the signs of ΔSsys and ΔSsurrounding for the following reaction
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g) ΔH°rxn = − 906 kJ - Answers ΔSsys > 0 and ΔSsurrounding >
0
Which of the following reactions could take place at the cathode of an electrochemical cell?
a) Cr2O7^2- to Cr^3+
b) F2 to F^-
Of the following, the entropy of which molecule would be the largest?
a) HCl (l)
b) HCl (g)
c) HBr (g)
d) HI (g) - Answers d
Ksp = 2.0 x 10-31 at 298 K for Al(OH)3(s).
What is the ΔG° at this temperature for the precipitation of Al(OH)3, according to the stoichiometric
equation: Al3+(aq) + 3OH-(aq) → Al(OH)3(s)? - Answers -175 kJ/mol
The Boltzmann formula is S = k ln W. A perfect crystal has a molar entropy of zero at absolute zero
because.... - Answers W=1
For a reaction, it was found that ΔH° = -140 kJ mol-1, and ΔSo = 120 J K-1 mol-1. This reaction would
be.... - Answers Spontaneous at all temperatures
Aluminum forms a layer of aluminum oxide when exposed to air, which protects the bulk metal from
further corrosion.
4Al(s) + 3O2(g) → 2Al2O3(s)
Calculate ΔG° for this reaction, given that ΔG°f of aluminum oxide is -1576.4 kJ/mol. - Answers -
3152.8 kJ/mol
What is the coefficient of iodide when the following equation is balanced in acidic solution? MnO4-
(aq) + I-(aq) → Mn2+(aq) + I2(aq) - Answers 10
Doubling all the coefficients in the equation for a cell reaction... - Answers doubles ΔG°, but does not
change E°
The standard voltage for a cell using the overall cell reaction
2Al(s) + 3I2(s) → 2Al3+(aq) + 6I-(aq) is +2.20V.
The cell voltage generated when [Al3+] = 0.150 M and [I-] = 4.5 x 10-3 M is... - Answers 2.35 V
The reaction rates of many spontaneous reactions are actually very slow. Which of these statements
is the best explanation for this observation?
a) Kp for the reaction is less than one.
b) ΔG° for the reaction is positive
c) the activation energy of the reaction is large
d) the entropy change is negative - Answers c
Complete and balance the following redox equation occurring in an acidic solution using the smallest
whole-number coefficients.
Sn + HNO3 ® SnO2 + NO2 + H2O
What is the coefficient of Sn in the balanced equation? - Answers 1
Given the information that:
2SO3 (g) ® 2S (s) + 3O2 (g)
ΔH° = 791.4 kJ
ΔG° = 742.2 kJ
Based on these values, calculate DHf° (kJ mol-1) for SO3? - Answers -395.7
Determine the change in entropy that occurs in the boiling of 18 g of water at 100 °C at ambient
pressure, ΔHvap = 40.7 kJ/mol - Answers -109 J/K
ΔG°f of water is - 237 kJ/mol. Determine if the water decomposition reaction, 2H2O(l) ⇌ O2 (g) +
H2(g) is exothermic or endothermic? - Answers Endothermic
Determine the signs of ΔSsys and ΔSsurrounding for the following reaction
4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(g) ΔH°rxn = − 906 kJ - Answers ΔSsys > 0 and ΔSsurrounding >
0
Which of the following reactions could take place at the cathode of an electrochemical cell?
a) Cr2O7^2- to Cr^3+
b) F2 to F^-
