Ultimate Chemistry Spring Final Exam Study Guide 2025: Expert-Verified Questions, Detailed Answer Explanations & Proven Strategies for Top Grades and A+ Success

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• Proven Strategies: Effective study and exam techniques for top performance.
• Comprehensive Coverage: Includes all essential chemistry topics for the 2025 spring final.
• Grade-Boosting Focus: Tailored to help students achieve A+ results.

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1. The enthalpy of vaporization of methanol (CH₃OH) is 35.3 kJ/mol at the boiling point of
64.2°C. Calculate the entropy change for methanol going from a liquid to vapor. a) 600
J/K·mol
b) 551 J/K·mol
c) 105 J/K·mol
d) -105 J/K·mol
e) -551 J/K·mol
Correct Answer: c) 105 J/K·mol
Rationale: Entropy change is calculated using ΔS = ΔH / T (in Kelvin). Converting 64.2°C to Kelvin:
64.2 + 273.15 = 337.35 K.
ΔS = (35.3 kJ/mol) / (337.35 K) = 105 J/K·mol.
2. Which of the following represents an increase in entropy?
a) Freezing of water
b) Boiling of water
c) Crystallization of salt from a supersaturated solution
d) The reaction 2 NO(g) → N2O2(g)
e) The reaction 2 H2(g) + O2(g) → 2 H2O(g)
Correct Answer: b) Boiling of water
Rationale: Entropy (S) is a measure of disorder. When water boils, it changes from liquid to gas,
increasing molecular motion and disorder, which increases entropy.
3. Calculate the standard entropy change for the reaction:
Cu(s) + ½ O₂(g) → CuO(s)
Given:
• S°[Cu(s)] = 33.15 J/K·mol
• S°[O₂(g)] = 205.14 J/K·mol
• S°[CuO(s)] = 42.63 J/K·mol
a) 195.66 J/K
b) 93.09 J/K
c) -45.28 J/K
d) -93.09 J/K
e) 195.66 J/K
Correct Answer: d) -93.09 J/K Rationale:
ΔS° = Σ S°(products) – Σ S°(reactants) ΔS°
= [42.63] – [33.15 + 0.5(205.14)] ΔS° =
42.63 – 135.72 = -93.09 J/K.