QUESTIONS ANDVERIFIED ANSWERS WITH RATIONALES
(GUARANTEED PASS)
This comprehensive final exam study guide features 200 meticulously
verified multiple-choice questions, accurate answers, and detailed
rationales for UNE CHEM 1011. It delivers complete cumulative coverage of
advanced chemical thermodynamics, dynamic equilibrium, complex buffer
systems, solubility products (\(K_{sp}\)), electrochemistry, and nuclear
chemistry. Expertly structured to optimize student scores, this resource
serves as an exceptional study tool that drives high-conversion sales
Module 1: Advanced Chemical Thermodynamics (Entropy & Free
Energy)
Question 1
A specific biochemical reaction exhibits a standard enthalpy change of
\(\Delta H^\circ = +62.4\text{ kJ/mol}\) and a standard entropy
change of \(\Delta S^\circ = +185\text{ J/(mol}\cdot\text{K)}\).
Calculate the threshold temperature above which this reaction becomes
thermodynamically spontaneous.
A. \(298\text{ K}\)
B. \(337\text{ K}\)
,C. \(0.337\text{ K}\)
D. \(2.96\text{ K}\)
VERIFIED ANSWER: B
EXPLANATION: A reaction reaches the threshold of spontaneity
when the standard Gibbs free energy change equals zero
(\(\Delta G^\circ = 0\)). Using the foundational
thermodynamic equation \(\Delta G^\circ = \Delta H^\circ -
T\Delta S^\circ\), we set the expression to \(0 = \Delta
H^\circ - T\Delta S^\circ\), which simplifies by algebraic
isolation to \(T = \frac{\Delta H^\circ}{\Delta S^\circ}\).
Before substituting the values, the entropy units must be
converted from Joules to Kilojoules to match the enthalpy
units: \(\Delta S^\circ = 185\text{ J/(mol}\cdot\text{K)} =
0.185\text{ kJ/(mol}\cdot\text{K)}\). Solving for absolute
temperature yields \(T = \frac{62.4\text{
kJ/mol}}{0.185\text{ kJ/(mol}\cdot\text{K)}} =
337.29\text{ K}\). Therefore, the reaction becomes
spontaneous (\(\Delta G^\circ < 0\)) at any temperature
strictly greater than \(337\text{ K}\).
Question 2
Which of the following statements correctly evaluates the signs of
\(\Delta H\) and \(\Delta S\) for the physical process of water vapor
,condensing into liquid droplets on a cold glass surface?
A. \(\Delta H > 0\) and \(\Delta S > 0\)
B. \(\Delta H > 0\) and \(\Delta S < 0\)
C. \(\Delta H < 0\) and \(\Delta S > 0\)
D. \(\Delta H < 0\) and \(\Delta S < 0\)
VERIFIED ANSWER: D
EXPLANATION: Condensation is a phase change where a gas
transitions into a more ordered liquid state. Because
intermolecular forces are forming between water molecules,
kinetic energy is released to the surrounding environment,
making the process exothermic (\(\Delta H < 0\)).
Concurrently, the positional freedom of the water molecules
decreases significantly as they move from a highly dispersed
gas phase to a restricted liquid phase, causing a definitive drop
in the system's molecular disorder or entropy (\(\Delta S <
0\)).
Question 3
The third law of thermodynamics provides a fundamental baseline for
assessing entropy. Which of the following states satisfies this law's
definition of zero entropy?
A. A pure, perfectly crystalline substance at a temperature of \(0\text{
K}\).
, B. A gaseous sample of an ideal gas at standard ambient temperature and
pressure.
C. A completely homogeneous aqueous liquid solution at \(273\text{ K}\).
D. Any element residing under its standard thermodynamic state at
\(298\text{ K}\).
VERIFIED ANSWER: A
EXPLANATION: The Third Law of Thermodynamics states that
the entropy of a pure, perfect crystalline substance is exactly
zero at absolute zero temperature (\(0\text{ K}\)). At this
theoretical point, all internal molecular motion stops
completely, eliminating vibrational, rotational, and translational
microstates, which results in a single unique microstate (\(W
= 1\), so \(S = k \ln W = 0\)).
Module 2: Dynamic Chemical Equilibrium & Le Chatelier's Principle
Question 4
Consider the industrial gas-phase equilibrium system: \(2\text{NO}_2(g)
\rightleftharpoons \text{N}_2\text{O}_4(g)\) where \(\Delta H^\circ =
-57.2\text{ kJ}\). Which of the following experimental perturbations will
shift the equilibrium position to favor the formation of more reactants?
A. Decreasing the volume of the reaction container at constant
temperature.
B. Injecting an inert gas into the vessel at a fixed, constant volume.