4 MAXE · 401 MEHC
★ ★
University of Wisconsin–Madison
W Department of Chemistry
EST. 1848
NUMEN LUMEN · THE WISCONSIN IDEA
Chem 104 Exam #4
G E N E RA L C H E M I ST RY I I — T H E R M O DY N A M I CS , G I B BS F R E E E N E R G Y &
E L E CT R O C H E M I ST RY
INSTITUTION University of Wisconsin–Madison PROGRAM Bachelor of Science — General
Chemistry II
COURSE CODE Chem 104 COURSE TITLE General Chemistry II
ACADEMIC YEAR EXAM TITLE Chem 104 Exam #4
TOTAL QUESTIONS 113 Questions FORMAT Multiple Choice — Select the
Single Best Answer
STUDY GUIDE INSTRUCTIONS
▸ This study guide covers thermodynamics, entropy, Gibbs free energy, electrochemistry, and redox
reactions for Chem 104 Exam 4.
▸ Each question tests one discrete concept, definition, or relationship from the course material.
▸ Select the single best answer. Correct answers and detailed rationales are provided for self-assessment.
▸ Pay careful attention to sign conventions for ΔG, ΔH, ΔS, q, w, and their relationship to spontaneity.
▸ All content reflects the standard General Chemistry II curriculum at UW–Madison.
, CHEM 104 — THERMODYNAMICS, FREE ENERGY &
Questions 1 – 113
ELECTROCHEMISTRY
1. When ΔG_sys = ΔH_sys − TΔS_sys is negative, the reaction is:
A. Nonspontaneous — reaction goes left, Q > K
B. Spontaneous — reaction goes right, Q < K
C. At equilibrium — Q = K
D. Endothermic only, regardless of ΔS
CORRECT ANSWER B — Spontaneous — reaction goes right, Q < K
RATIONALE A negative ΔG indicates a spontaneous process in the forward direction. The
reaction proceeds toward products (shifts right), and Q < K. This is the
fundamental criterion for spontaneity at constant T and P: ΔG < 0 → spontaneous;
ΔG > 0 → nonspontaneous (Option A); ΔG = 0 → equilibrium (Option C).
Spontaneous processes can be endothermic if entropy increase is sufficient to
make ΔG negative.
2. Assuming ΔH° and ΔS° are constant with temperature, which equation directly shows how
Gibbs free energy depends on temperature?
A. ΔG = −RT ln K
B. ΔG = ΔH − TΔS
C. ΔG = ΔG° + RT ln Q
D. ΔG = w_max
CORRECT ANSWER B — ΔG = ΔH − TΔS
RATIONALE ΔG = ΔH − TΔS explicitly shows temperature dependence — as T increases, the
−TΔS term becomes more significant. Option A relates ΔG° to K. Option C corrects
for non-standard conditions. Option D states ΔG equals maximum non-PV work.
Only ΔG = ΔH − TΔS isolates temperature as the variable governing spontaneity,
allowing prediction of how favorability changes with T based on signs of ΔH and
ΔS.
,3. Thermodynamics is defined as the study of:
A. Reaction rates and mechanisms
B. Energies and how energy is transferred
C. Molecular structure and bonding
D. Chemical equilibrium exclusively
CORRECT ANSWER B — Energies and how energy is transferred
RATIONALE Thermodynamics studies energy and its transformations — how energy transfers
as heat and work, determining direction and extent of processes. Reaction rates
(Option A) belong to kinetics. Molecular structure (Option C) is quantum
mechanics/spectroscopy. Equilibrium (Option D) is one application.
Thermodynamics answers "Can it happen?" while kinetics answers "How fast?"
4. The two major properties that govern thermodynamics are:
A. Temperature and pressure
B. Energy (E) and Entropy (S)
C. Work and heat
D. Volume and moles
CORRECT ANSWER B — Energy (E) and Entropy (S)
RATIONALE Energy describes stability (lower E = more favorable) and entropy describes
disorder/probability (higher S = more favorable). Together they determine
spontaneity via ΔG = ΔH − TΔS. Temperature and pressure are state variables.
Work and heat are forms of energy transfer. Volume and moles are extensive
properties. E and S are the fundamental thermodynamic drivers.
, 5. Choose the statement that is TRUE:
A. When K < 1, ΔG° < 0
B. When K < 1, ΔG° > 0
C. When K < 1, ΔG° = 0
D. K and ΔG° are unrelated
CORRECT ANSWER B — When K < 1, ΔG° > 0
RATIONALE ΔG° = −RT ln K. When K < 1, ln K is negative, so ΔG° = −RT(negative) = positive. A
positive ΔG° means nonspontaneous under standard conditions, equilibrium lies
left (reactants favored). When K > 1, ΔG° is negative. When K = 1, ΔG° = 0. K and ΔG°
are fundamentally connected by this logarithmic relationship.
6. Energy (E) in thermodynamics describes what property?
A. Disorder and randomness of a system
B. Stability — lower energy is more favorable and indicates greater stability
C. The rate at which a reaction occurs
D. The color of a chemical compound
CORRECT ANSWER B — Stability — lower energy is more favorable and indicates greater
stability
RATIONALE Energy describes stability — systems naturally move toward lower energy states
because they are more stable. This drives exothermic reactions (ΔH < 0). Disorder
(Option A) is entropy (S). Reaction rate (Option C) is kinetics. Physical properties
like color (Option D) are not thermodynamic governing properties. Energy and
entropy together determine spontaneity.
★ ★
University of Wisconsin–Madison
W Department of Chemistry
EST. 1848
NUMEN LUMEN · THE WISCONSIN IDEA
Chem 104 Exam #4
G E N E RA L C H E M I ST RY I I — T H E R M O DY N A M I CS , G I B BS F R E E E N E R G Y &
E L E CT R O C H E M I ST RY
INSTITUTION University of Wisconsin–Madison PROGRAM Bachelor of Science — General
Chemistry II
COURSE CODE Chem 104 COURSE TITLE General Chemistry II
ACADEMIC YEAR EXAM TITLE Chem 104 Exam #4
TOTAL QUESTIONS 113 Questions FORMAT Multiple Choice — Select the
Single Best Answer
STUDY GUIDE INSTRUCTIONS
▸ This study guide covers thermodynamics, entropy, Gibbs free energy, electrochemistry, and redox
reactions for Chem 104 Exam 4.
▸ Each question tests one discrete concept, definition, or relationship from the course material.
▸ Select the single best answer. Correct answers and detailed rationales are provided for self-assessment.
▸ Pay careful attention to sign conventions for ΔG, ΔH, ΔS, q, w, and their relationship to spontaneity.
▸ All content reflects the standard General Chemistry II curriculum at UW–Madison.
, CHEM 104 — THERMODYNAMICS, FREE ENERGY &
Questions 1 – 113
ELECTROCHEMISTRY
1. When ΔG_sys = ΔH_sys − TΔS_sys is negative, the reaction is:
A. Nonspontaneous — reaction goes left, Q > K
B. Spontaneous — reaction goes right, Q < K
C. At equilibrium — Q = K
D. Endothermic only, regardless of ΔS
CORRECT ANSWER B — Spontaneous — reaction goes right, Q < K
RATIONALE A negative ΔG indicates a spontaneous process in the forward direction. The
reaction proceeds toward products (shifts right), and Q < K. This is the
fundamental criterion for spontaneity at constant T and P: ΔG < 0 → spontaneous;
ΔG > 0 → nonspontaneous (Option A); ΔG = 0 → equilibrium (Option C).
Spontaneous processes can be endothermic if entropy increase is sufficient to
make ΔG negative.
2. Assuming ΔH° and ΔS° are constant with temperature, which equation directly shows how
Gibbs free energy depends on temperature?
A. ΔG = −RT ln K
B. ΔG = ΔH − TΔS
C. ΔG = ΔG° + RT ln Q
D. ΔG = w_max
CORRECT ANSWER B — ΔG = ΔH − TΔS
RATIONALE ΔG = ΔH − TΔS explicitly shows temperature dependence — as T increases, the
−TΔS term becomes more significant. Option A relates ΔG° to K. Option C corrects
for non-standard conditions. Option D states ΔG equals maximum non-PV work.
Only ΔG = ΔH − TΔS isolates temperature as the variable governing spontaneity,
allowing prediction of how favorability changes with T based on signs of ΔH and
ΔS.
,3. Thermodynamics is defined as the study of:
A. Reaction rates and mechanisms
B. Energies and how energy is transferred
C. Molecular structure and bonding
D. Chemical equilibrium exclusively
CORRECT ANSWER B — Energies and how energy is transferred
RATIONALE Thermodynamics studies energy and its transformations — how energy transfers
as heat and work, determining direction and extent of processes. Reaction rates
(Option A) belong to kinetics. Molecular structure (Option C) is quantum
mechanics/spectroscopy. Equilibrium (Option D) is one application.
Thermodynamics answers "Can it happen?" while kinetics answers "How fast?"
4. The two major properties that govern thermodynamics are:
A. Temperature and pressure
B. Energy (E) and Entropy (S)
C. Work and heat
D. Volume and moles
CORRECT ANSWER B — Energy (E) and Entropy (S)
RATIONALE Energy describes stability (lower E = more favorable) and entropy describes
disorder/probability (higher S = more favorable). Together they determine
spontaneity via ΔG = ΔH − TΔS. Temperature and pressure are state variables.
Work and heat are forms of energy transfer. Volume and moles are extensive
properties. E and S are the fundamental thermodynamic drivers.
, 5. Choose the statement that is TRUE:
A. When K < 1, ΔG° < 0
B. When K < 1, ΔG° > 0
C. When K < 1, ΔG° = 0
D. K and ΔG° are unrelated
CORRECT ANSWER B — When K < 1, ΔG° > 0
RATIONALE ΔG° = −RT ln K. When K < 1, ln K is negative, so ΔG° = −RT(negative) = positive. A
positive ΔG° means nonspontaneous under standard conditions, equilibrium lies
left (reactants favored). When K > 1, ΔG° is negative. When K = 1, ΔG° = 0. K and ΔG°
are fundamentally connected by this logarithmic relationship.
6. Energy (E) in thermodynamics describes what property?
A. Disorder and randomness of a system
B. Stability — lower energy is more favorable and indicates greater stability
C. The rate at which a reaction occurs
D. The color of a chemical compound
CORRECT ANSWER B — Stability — lower energy is more favorable and indicates greater
stability
RATIONALE Energy describes stability — systems naturally move toward lower energy states
because they are more stable. This drives exothermic reactions (ΔH < 0). Disorder
(Option A) is entropy (S). Reaction rate (Option C) is kinetics. Physical properties
like color (Option D) are not thermodynamic governing properties. Energy and
entropy together determine spontaneity.
