,Portage Learning CHEM 103 General
Chemistry I Module 6 Exam
Question 1
A reaction occurring in an insulated beaker causes the temperature of the surrounding
water to rise. How is this chemical reaction classified, and what is the sign of its
enthalpy change (\(\Delta H\))?
A) Endothermic, \(\Delta H > 0\)
B) Exothermic, \(\Delta H > 0\)
C) Exothermic, \(\Delta H < 0\)
D) Endothermic, \(\Delta H < 0\)
Answer: C
Rationale: An increase in the temperature of the surrounding water indicates that the
chemical system is releasing thermal energy into its environment. Processes that
liberate heat are classified as exothermic, and by thermodynamic convention, their
enthalpy change values are negative (\(\Delta H < 0\)).
Question 2
Which of the following physical phase transformations represents an endothermic
process?
A) Condensation of water vapor
B) Freezing of liquid ethanol
C) Deposition of carbon dioxide gas
D) Sublimation of solid iodine
Answer: D
Rationale: Endothermic changes require an absolute absorption of energy from the
surroundings to overcome intermolecular attractive forces. Sublimation converts a solid
directly into a gas, which demands a substantial input of energy to completely disrupt
the structured lattice of the solid state.
, Question 3
How much heat energy (in Joules) is required to raise the temperature of \(25.0\text{ g}\)
of pure liquid water from \(20.0^{\circ }\text{C}\) to \(60.0^{\circ }\text{C}\)? (The specific
heat capacity of water is \(4.184\text{ J/g}\cdot^\circ\text{C}\)).
A) \(4,184\text{ J}\)
B) \(2,092\text{ J}\)
C) \(6,276\text{ J}\)
D) \(1,046\text{ J}\)
Answer: A
Rationale: Use the specific heat equation: \(q = m \cdot c \cdot \Delta T\). Here, \(\Delta
T = T_{\text{final}} - T_{\text{initial}} = 60.0^\circ\text{C} - 20.0^\circ\text{C} =
40.0^\circ\text{C}\). Substituting the numbers: \(q = 25.0\text{ g} \times 4.184\text{
J/g}\cdot^\circ\text{C} \times 40.0^\circ\text{C} = 4,184\text{ J}\).
Question 4
A \(50.0\text{ g}\) piece of an unknown metal at \(100.0^{\circ }\text{C}\) is dropped into
an insulated calorimeter containing water. The metal loses \(1,200\text{ J}\) of heat
energy to the water. What is the value of \(q_{\text{metal}}\) and \(q_{\text{water}}\)?
A) \(q_{\text{metal}} = +1,200\text{ J}\), \(q_{\text{water}} = -1,200\text{ J}\)
B) \(q_{\text{metal}} = -1,200\text{ J}\), \(q_{\text{water}} = +1,200\text{ J}\)
C) \(q_{\text{metal}} = -1,200\text{ J}\), \(q_{\text{water}} = -1,200\text{ J}\)
D) \(q_{\text{metal}} = +1,200\text{ J}\), \(q_{\text{water}} = +1,200\text{ J}\)
Answer: B
Rationale: According to the first law of thermodynamics, energy cannot be created or
destroyed. In an isolated calorimeter system, the heat lost by the system must equal the
heat gained by the surroundings (\(q_{\text{metal}} = -q_{\text{water}}\)). Because the
metal sheds energy, its value is negative (\(-1,200\text{ J}\)), and the water absorbing
that exact energy is positive (\(+1,200\text{ J}\)).
Question 5
Given the target reaction: \(2\text{A}\rightarrow 2\text{B}\), calculate the overall \(\Delta
H\) using the following data:
Reaction 1: \(\text{B}\rightarrow \text{A}\) with \(\Delta H = -150\text{ kJ}\).
A) \(-150\text{ kJ}\)
B) \(+150\text{ kJ}\)
C) \(-300\text{ kJ}\)
D) \(+300\text{ kJ}\)
Chemistry I Module 6 Exam
Question 1
A reaction occurring in an insulated beaker causes the temperature of the surrounding
water to rise. How is this chemical reaction classified, and what is the sign of its
enthalpy change (\(\Delta H\))?
A) Endothermic, \(\Delta H > 0\)
B) Exothermic, \(\Delta H > 0\)
C) Exothermic, \(\Delta H < 0\)
D) Endothermic, \(\Delta H < 0\)
Answer: C
Rationale: An increase in the temperature of the surrounding water indicates that the
chemical system is releasing thermal energy into its environment. Processes that
liberate heat are classified as exothermic, and by thermodynamic convention, their
enthalpy change values are negative (\(\Delta H < 0\)).
Question 2
Which of the following physical phase transformations represents an endothermic
process?
A) Condensation of water vapor
B) Freezing of liquid ethanol
C) Deposition of carbon dioxide gas
D) Sublimation of solid iodine
Answer: D
Rationale: Endothermic changes require an absolute absorption of energy from the
surroundings to overcome intermolecular attractive forces. Sublimation converts a solid
directly into a gas, which demands a substantial input of energy to completely disrupt
the structured lattice of the solid state.
, Question 3
How much heat energy (in Joules) is required to raise the temperature of \(25.0\text{ g}\)
of pure liquid water from \(20.0^{\circ }\text{C}\) to \(60.0^{\circ }\text{C}\)? (The specific
heat capacity of water is \(4.184\text{ J/g}\cdot^\circ\text{C}\)).
A) \(4,184\text{ J}\)
B) \(2,092\text{ J}\)
C) \(6,276\text{ J}\)
D) \(1,046\text{ J}\)
Answer: A
Rationale: Use the specific heat equation: \(q = m \cdot c \cdot \Delta T\). Here, \(\Delta
T = T_{\text{final}} - T_{\text{initial}} = 60.0^\circ\text{C} - 20.0^\circ\text{C} =
40.0^\circ\text{C}\). Substituting the numbers: \(q = 25.0\text{ g} \times 4.184\text{
J/g}\cdot^\circ\text{C} \times 40.0^\circ\text{C} = 4,184\text{ J}\).
Question 4
A \(50.0\text{ g}\) piece of an unknown metal at \(100.0^{\circ }\text{C}\) is dropped into
an insulated calorimeter containing water. The metal loses \(1,200\text{ J}\) of heat
energy to the water. What is the value of \(q_{\text{metal}}\) and \(q_{\text{water}}\)?
A) \(q_{\text{metal}} = +1,200\text{ J}\), \(q_{\text{water}} = -1,200\text{ J}\)
B) \(q_{\text{metal}} = -1,200\text{ J}\), \(q_{\text{water}} = +1,200\text{ J}\)
C) \(q_{\text{metal}} = -1,200\text{ J}\), \(q_{\text{water}} = -1,200\text{ J}\)
D) \(q_{\text{metal}} = +1,200\text{ J}\), \(q_{\text{water}} = +1,200\text{ J}\)
Answer: B
Rationale: According to the first law of thermodynamics, energy cannot be created or
destroyed. In an isolated calorimeter system, the heat lost by the system must equal the
heat gained by the surroundings (\(q_{\text{metal}} = -q_{\text{water}}\)). Because the
metal sheds energy, its value is negative (\(-1,200\text{ J}\)), and the water absorbing
that exact energy is positive (\(+1,200\text{ J}\)).
Question 5
Given the target reaction: \(2\text{A}\rightarrow 2\text{B}\), calculate the overall \(\Delta
H\) using the following data:
Reaction 1: \(\text{B}\rightarrow \text{A}\) with \(\Delta H = -150\text{ kJ}\).
A) \(-150\text{ kJ}\)
B) \(+150\text{ kJ}\)
C) \(-300\text{ kJ}\)
D) \(+300\text{ kJ}\)
