CHEM 121 MODULE 7:
THERMOCHEMISTRY AND ENERGY
EXAM QUESTIONS AND ANSWERS
2026/2027 UPDATE || 100% GUARANTEED
PASS
1. A system undergoes a process where it absorbs 450 J of heat and performs 120 J of work on
the surroundings. What is the change in internal energy (ΔU)?
A. 330 J
B. 570 J
C. -330 J
D. -570 J
Answer: A
Conceptual Explanation: According to the first law of thermodynamics, ΔU = q + w. Since
heat is absorbed, q = +450 J. Since work is done by the system, w = -120 J. ΔU = 450 - 120 =
330 J.
2. Which of the following is considered a state function?
A. Enthalpy (H)
B. Work (w)
,C. Heat (q)
D. Distance traveled
Answer: A
Conceptual Explanation: A state function is a property whose value depends only on the
current state of the system, not the path taken to reach it. Enthalpy, Internal Energy, and
Pressure are state functions, while heat and work are path functions.
3. How much heat is required to raise the temperature of 50.0 g of liquid water from 25.0°C
to 45.0°C? (Specific heat of water = 4.184 J/g°C)
A. 2092 J
B. 4184 J
C. 1046 J
D. 5230 J
Answer: B
Conceptual Explanation: Using the formula q = mcΔT: q = (50.0 g)(4.184 J/g°C)(45.0 -
25.0) = 50 * 4.184 * 20 = 4184 J.
4. Calculate the work done (in Joules) by a gas as it expands from 2.0 L to 5.0 L against a
constant external pressure of 1.5 atm. (1 L·atm = 101.3 J)
A. -455.85 J
B. 455.85 J
, C. -3.04 J
D. -151.95 J
Answer: A
Conceptual Explanation: Work w = -PΔV. w = -(1.5 atm)(5.0 L - 2.0 L) = -4.5 L·atm.
Converting to Joules: -4.5 * 101.3 = -455.85 J.
5. In an exothermic reaction, which of the following is true?
A. ΔH is positive and heat is absorbed.
B. ΔH is negative and heat is released.
C. The surroundings lose energy.
D. The enthalpy of products is greater than the enthalpy of reactants.
Answer: B
Conceptual Explanation: In an exothermic reaction, the system releases heat to the
surroundings, meaning ΔH < 0 (negative).
6. Given the reaction: 2H2(g) + O2(g) -> 2H2O(l), ΔH = -572 kJ. What is the enthalpy change for
the production of 1.00 mole of H2O(l)?
A. -572 kJ
B. -286 kJ
C. +286 kJ
THERMOCHEMISTRY AND ENERGY
EXAM QUESTIONS AND ANSWERS
2026/2027 UPDATE || 100% GUARANTEED
PASS
1. A system undergoes a process where it absorbs 450 J of heat and performs 120 J of work on
the surroundings. What is the change in internal energy (ΔU)?
A. 330 J
B. 570 J
C. -330 J
D. -570 J
Answer: A
Conceptual Explanation: According to the first law of thermodynamics, ΔU = q + w. Since
heat is absorbed, q = +450 J. Since work is done by the system, w = -120 J. ΔU = 450 - 120 =
330 J.
2. Which of the following is considered a state function?
A. Enthalpy (H)
B. Work (w)
,C. Heat (q)
D. Distance traveled
Answer: A
Conceptual Explanation: A state function is a property whose value depends only on the
current state of the system, not the path taken to reach it. Enthalpy, Internal Energy, and
Pressure are state functions, while heat and work are path functions.
3. How much heat is required to raise the temperature of 50.0 g of liquid water from 25.0°C
to 45.0°C? (Specific heat of water = 4.184 J/g°C)
A. 2092 J
B. 4184 J
C. 1046 J
D. 5230 J
Answer: B
Conceptual Explanation: Using the formula q = mcΔT: q = (50.0 g)(4.184 J/g°C)(45.0 -
25.0) = 50 * 4.184 * 20 = 4184 J.
4. Calculate the work done (in Joules) by a gas as it expands from 2.0 L to 5.0 L against a
constant external pressure of 1.5 atm. (1 L·atm = 101.3 J)
A. -455.85 J
B. 455.85 J
, C. -3.04 J
D. -151.95 J
Answer: A
Conceptual Explanation: Work w = -PΔV. w = -(1.5 atm)(5.0 L - 2.0 L) = -4.5 L·atm.
Converting to Joules: -4.5 * 101.3 = -455.85 J.
5. In an exothermic reaction, which of the following is true?
A. ΔH is positive and heat is absorbed.
B. ΔH is negative and heat is released.
C. The surroundings lose energy.
D. The enthalpy of products is greater than the enthalpy of reactants.
Answer: B
Conceptual Explanation: In an exothermic reaction, the system releases heat to the
surroundings, meaning ΔH < 0 (negative).
6. Given the reaction: 2H2(g) + O2(g) -> 2H2O(l), ΔH = -572 kJ. What is the enthalpy change for
the production of 1.00 mole of H2O(l)?
A. -572 kJ
B. -286 kJ
C. +286 kJ
