,
, Portage Learning CHEM 103 General
Chemistry I Module 6 Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
A reaction takes place in an aqueous solution inside a calorimeter. The temperature of
the water increases from \(22.0^{\circ }\text{C}\) to \(28.5^{\circ }\text{C}\). How is this
chemical reaction classified, and what is the sign of \(\Delta H_{\text{rxn}}\)?
A) Endothermic, \(\Delta H > 0\)
B) Exothermic, \(\Delta H < 0\)
C) Endothermic, \(\Delta H < 0\)
D) Exothermic, \(\Delta H > 0\)
Answer: B
Rationale: Because the temperature of the surrounding water increased, the chemical
reaction (the system) released thermal energy into its environment. A process that
releases heat is exothermic, and by convention, exothermic processes have a negative
enthalpy change (\(\Delta H < 0\)).
Question 2
Which of the following processes represents an endothermic phase change?
A) Water vapor condensing into liquid rain
B) Liquid water freezing into ice cubes
C) Molten iron solidifying in a mold
D) Liquid alcohol vaporizing into a gas
Answer: D
Rationale: Endothermic phase changes require an influx of thermal energy from the
surroundings to break intermolecular forces. Vaporization (liquid to gas) requires
heating, making it endothermic. Condensation and freezing/solidification release heat,
making them exothermic.
, Portage Learning CHEM 103 General
Chemistry I Module 6 Exam | 2025
Updated Edition with 100% Verified
Answers
Question 1
A reaction takes place in an aqueous solution inside a calorimeter. The temperature of
the water increases from \(22.0^{\circ }\text{C}\) to \(28.5^{\circ }\text{C}\). How is this
chemical reaction classified, and what is the sign of \(\Delta H_{\text{rxn}}\)?
A) Endothermic, \(\Delta H > 0\)
B) Exothermic, \(\Delta H < 0\)
C) Endothermic, \(\Delta H < 0\)
D) Exothermic, \(\Delta H > 0\)
Answer: B
Rationale: Because the temperature of the surrounding water increased, the chemical
reaction (the system) released thermal energy into its environment. A process that
releases heat is exothermic, and by convention, exothermic processes have a negative
enthalpy change (\(\Delta H < 0\)).
Question 2
Which of the following processes represents an endothermic phase change?
A) Water vapor condensing into liquid rain
B) Liquid water freezing into ice cubes
C) Molten iron solidifying in a mold
D) Liquid alcohol vaporizing into a gas
Answer: D
Rationale: Endothermic phase changes require an influx of thermal energy from the
surroundings to break intermolecular forces. Vaporization (liquid to gas) requires
heating, making it endothermic. Condensation and freezing/solidification release heat,
making them exothermic.
