CHEM 121 MODULE 6 EXAM:
THERMODYNAMICS AND
THERMOCHEMISTRY QUESTIONS AND
ANSWERS 2026/2027 UPDATE || 100%
GUARANTEED PASS
1. According to the First Law of Thermodynamics, which of the following expressions correctly
represents the change in internal energy (ΔU) of a system?
A. ΔU = q - w
B. ΔU = q + w
C. ΔU = H + PV
D. ΔU = TS - H
Answer: B
Conceptual Explanation: The First Law of Thermodynamics states that the change in
internal energy is the sum of the heat added to the system and the work done on the
system.
2. In a process where the system performs 50 J of work and absorbs 20 J of heat, what is the
change in internal energy?
A. 70 J
,B. 30 J
C. -30 J
D. -70 J
Answer: C
Conceptual Explanation: ΔU = q + w. Here, q = +20 J (absorbed) and w = -50 J (done by
system). ΔU = 20 - 50 = -30 J.
3. Which of the following is considered a state function?
A. Heat (q)
B. Work (w)
C. Enthalpy (H)
D. Distance traveled
Answer: C
Conceptual Explanation: State functions depend only on the current state of the system,
not the path taken. Enthalpy, temperature, and pressure are state functions; heat and work
are path functions.
4. For an exothermic reaction occurring at constant pressure, what is the sign of ΔH?
A. Positive
B. Zero
, C. Negative
D. Undetermined
Answer: C
Conceptual Explanation: Exothermic reactions release heat to the surroundings, meaning
the enthalpy of the products is lower than the reactants, resulting in a negative ΔH.
5. What is the standard enthalpy of formation (ΔHf°) for an element in its most stable form at
25°C and 1 atm?
A. 0 kJ/mol
B. Variable depending on the element
C. 9.8 kJ/mol
D. 1.0 kJ/mol
Answer: A
Conceptual Explanation: By convention, the standard enthalpy of formation for any
element in its most stable allotropic state at standard conditions is defined as zero.
6. How much heat is required to raise the temperature of 50.0 g of water from 20.0°C to
60.0°C? (Specific heat of water = 4.184 J/g°C)
A. 10,460 J
B. 12,552 J
C. 4,184 J
THERMODYNAMICS AND
THERMOCHEMISTRY QUESTIONS AND
ANSWERS 2026/2027 UPDATE || 100%
GUARANTEED PASS
1. According to the First Law of Thermodynamics, which of the following expressions correctly
represents the change in internal energy (ΔU) of a system?
A. ΔU = q - w
B. ΔU = q + w
C. ΔU = H + PV
D. ΔU = TS - H
Answer: B
Conceptual Explanation: The First Law of Thermodynamics states that the change in
internal energy is the sum of the heat added to the system and the work done on the
system.
2. In a process where the system performs 50 J of work and absorbs 20 J of heat, what is the
change in internal energy?
A. 70 J
,B. 30 J
C. -30 J
D. -70 J
Answer: C
Conceptual Explanation: ΔU = q + w. Here, q = +20 J (absorbed) and w = -50 J (done by
system). ΔU = 20 - 50 = -30 J.
3. Which of the following is considered a state function?
A. Heat (q)
B. Work (w)
C. Enthalpy (H)
D. Distance traveled
Answer: C
Conceptual Explanation: State functions depend only on the current state of the system,
not the path taken. Enthalpy, temperature, and pressure are state functions; heat and work
are path functions.
4. For an exothermic reaction occurring at constant pressure, what is the sign of ΔH?
A. Positive
B. Zero
, C. Negative
D. Undetermined
Answer: C
Conceptual Explanation: Exothermic reactions release heat to the surroundings, meaning
the enthalpy of the products is lower than the reactants, resulting in a negative ΔH.
5. What is the standard enthalpy of formation (ΔHf°) for an element in its most stable form at
25°C and 1 atm?
A. 0 kJ/mol
B. Variable depending on the element
C. 9.8 kJ/mol
D. 1.0 kJ/mol
Answer: A
Conceptual Explanation: By convention, the standard enthalpy of formation for any
element in its most stable allotropic state at standard conditions is defined as zero.
6. How much heat is required to raise the temperature of 50.0 g of water from 20.0°C to
60.0°C? (Specific heat of water = 4.184 J/g°C)
A. 10,460 J
B. 12,552 J
C. 4,184 J
