,Verified CHEM 103 Module 7 Exam-General
1. The Law of Conservation of Energy states that:
A) Energy can be created but not destroyed
B) Energy can be destroyed but not created
C) Energy cannot be created or destroyed, only transformed from one form to another
D) Energy is always lost as heat in chemical reactions
Correct Answer: C) Energy cannot be created or destroyed, only transformed from one form to
another
Rationale: The Law of Conservation of Energy is a fundamental principle stating that energy cannot be
created or destroyed; it can only be transformed from one form to another. Option A and B are
incorrect because energy is neither created nor destroyed. Option D is incorrect because energy can
be transformed into other forms, not always lost as heat.
2. A chemical reaction that releases heat to its surroundings is classified as:
A) Endothermic
B) Exothermic
C) Isothermic
D) Adiabatic
Correct Answer: B) Exothermic
Rationale: Exothermic reactions release energy (usually as heat) to the surroundings, causing the
surroundings to warm. The sign of ΔH is negative for exothermic reactions. Endothermic (A) absorbs
heat, isothermic (C) means constant temperature, and adiabatic (D) means no heat exchange.
3. Which of the following best defines enthalpy (H)?
A) The total kinetic energy of all molecules in a system
B) The heat content of a system at constant pressure
C) The measure of disorder in a system
D) The energy required to break all bonds in one mole of substance
Correct Answer: B) The heat content of a system at constant pressure
,Rationale: Enthalpy is defined as the heat content of a system at constant pressure, represented by H
in thermochemical equations. Option A describes kinetic energy, C describes entropy, and D describes
bond energy.
4. A reaction releases 850 kJ of energy. What is the sign of ΔH for this reaction?
A) Positive; the reaction is endothermic
B) Negative; the reaction is exothermic
C) Positive; the reaction is exothermic
D) Negative; the reaction is endothermic
Correct Answer: B) Negative; the reaction is exothermic
Rationale: When energy is released by a reaction, ΔH is negative and the reaction is classified as
exothermic. The negative sign indicates that energy leaves the system and enters the surroundings.
Option A describes endothermic (ΔH > 0), C has the wrong sign convention, and D is incorrect.
5. Calculate the heat required to raise the temperature of 50.0 g of water from 25.0°C to 75.0°C.
(Specific heat of water = 4.184 J/g·°C)
A) 5,230 J
B) 10,460 J
C) 15,690 J
D) 20,920 J
Correct Answer: B) 10,460 J
Rationale: q = m × c × ΔT = 50.0 g × 4.184 J/g·°C × (75.0 - 25.0)°C = 50.0 × 4.184 × 50.0 = 10,460 J.
Option A is for a 25°C change, C is for a 75°C change, and D is for a 100°C change.
6. A 1.475 g sample of water is heated from 22°C to 35°C. The specific heat of water is 4.18 J/g°C.
Calculate the heat absorbed.
A) 45.2 J
B) 80.1 J
C) 120.0 J
D) 4075.5 J
Correct Answer: B) 80.1 J
, Rationale: q = m × c × ΔT = 1.475 g × 4.18 J/g°C × (35 - 22)°C = 1.475 × 4.18 × 13 = 80.1 J. Option A is
incorrect, C is incorrect, and D is the calculation if m = 75 g (not 1.475 g).
7. A 120 g metal sample absorbs 1560 J of heat and its temperature rises from 25°C to 40°C. Calculate
the specific heat capacity.
A) 0.433 J/g°C
B) 0.867 J/g°C
C) 1.30 J/g°C
D) 2.60 J/g°C
Correct Answer: B) 0.867 J/g°C
Rationale: c = q / (m × ΔT) = 1560 J / (120 g × 15°C) = = 0.867 J/g°C. Option A is half the
correct value, C is 50% higher, and D is triple the correct value.
8. If 150 kJ of heat is released during a reaction, what is the enthalpy change (ΔH)?
A) +150 kJ
B) -150 kJ
C) 0 kJ
D) +75 kJ
Correct Answer: B) -150 kJ
Rationale: Heat released indicates an exothermic reaction, which has a negative ΔH. Therefore, ΔH = -
150 kJ. Option A has the wrong sign (would be for heat absorbed), C would mean no heat change, and
D is incorrect.
9. A reaction releases 8500 J of heat in a calorimeter containing 200 g of water. Calculate the
temperature change of the water. (c = 4.18 J/g°C)
A) 5.08°C
B) 10.17°C
C) 20.34°C
D) 40.68°C
Correct Answer: B) 10.17°C
1. The Law of Conservation of Energy states that:
A) Energy can be created but not destroyed
B) Energy can be destroyed but not created
C) Energy cannot be created or destroyed, only transformed from one form to another
D) Energy is always lost as heat in chemical reactions
Correct Answer: C) Energy cannot be created or destroyed, only transformed from one form to
another
Rationale: The Law of Conservation of Energy is a fundamental principle stating that energy cannot be
created or destroyed; it can only be transformed from one form to another. Option A and B are
incorrect because energy is neither created nor destroyed. Option D is incorrect because energy can
be transformed into other forms, not always lost as heat.
2. A chemical reaction that releases heat to its surroundings is classified as:
A) Endothermic
B) Exothermic
C) Isothermic
D) Adiabatic
Correct Answer: B) Exothermic
Rationale: Exothermic reactions release energy (usually as heat) to the surroundings, causing the
surroundings to warm. The sign of ΔH is negative for exothermic reactions. Endothermic (A) absorbs
heat, isothermic (C) means constant temperature, and adiabatic (D) means no heat exchange.
3. Which of the following best defines enthalpy (H)?
A) The total kinetic energy of all molecules in a system
B) The heat content of a system at constant pressure
C) The measure of disorder in a system
D) The energy required to break all bonds in one mole of substance
Correct Answer: B) The heat content of a system at constant pressure
,Rationale: Enthalpy is defined as the heat content of a system at constant pressure, represented by H
in thermochemical equations. Option A describes kinetic energy, C describes entropy, and D describes
bond energy.
4. A reaction releases 850 kJ of energy. What is the sign of ΔH for this reaction?
A) Positive; the reaction is endothermic
B) Negative; the reaction is exothermic
C) Positive; the reaction is exothermic
D) Negative; the reaction is endothermic
Correct Answer: B) Negative; the reaction is exothermic
Rationale: When energy is released by a reaction, ΔH is negative and the reaction is classified as
exothermic. The negative sign indicates that energy leaves the system and enters the surroundings.
Option A describes endothermic (ΔH > 0), C has the wrong sign convention, and D is incorrect.
5. Calculate the heat required to raise the temperature of 50.0 g of water from 25.0°C to 75.0°C.
(Specific heat of water = 4.184 J/g·°C)
A) 5,230 J
B) 10,460 J
C) 15,690 J
D) 20,920 J
Correct Answer: B) 10,460 J
Rationale: q = m × c × ΔT = 50.0 g × 4.184 J/g·°C × (75.0 - 25.0)°C = 50.0 × 4.184 × 50.0 = 10,460 J.
Option A is for a 25°C change, C is for a 75°C change, and D is for a 100°C change.
6. A 1.475 g sample of water is heated from 22°C to 35°C. The specific heat of water is 4.18 J/g°C.
Calculate the heat absorbed.
A) 45.2 J
B) 80.1 J
C) 120.0 J
D) 4075.5 J
Correct Answer: B) 80.1 J
, Rationale: q = m × c × ΔT = 1.475 g × 4.18 J/g°C × (35 - 22)°C = 1.475 × 4.18 × 13 = 80.1 J. Option A is
incorrect, C is incorrect, and D is the calculation if m = 75 g (not 1.475 g).
7. A 120 g metal sample absorbs 1560 J of heat and its temperature rises from 25°C to 40°C. Calculate
the specific heat capacity.
A) 0.433 J/g°C
B) 0.867 J/g°C
C) 1.30 J/g°C
D) 2.60 J/g°C
Correct Answer: B) 0.867 J/g°C
Rationale: c = q / (m × ΔT) = 1560 J / (120 g × 15°C) = = 0.867 J/g°C. Option A is half the
correct value, C is 50% higher, and D is triple the correct value.
8. If 150 kJ of heat is released during a reaction, what is the enthalpy change (ΔH)?
A) +150 kJ
B) -150 kJ
C) 0 kJ
D) +75 kJ
Correct Answer: B) -150 kJ
Rationale: Heat released indicates an exothermic reaction, which has a negative ΔH. Therefore, ΔH = -
150 kJ. Option A has the wrong sign (would be for heat absorbed), C would mean no heat change, and
D is incorrect.
9. A reaction releases 8500 J of heat in a calorimeter containing 200 g of water. Calculate the
temperature change of the water. (c = 4.18 J/g°C)
A) 5.08°C
B) 10.17°C
C) 20.34°C
D) 40.68°C
Correct Answer: B) 10.17°C
