Complete Practice Question Bank
MCQs + Fill in the Blanks + True/False + Assertion Reason + Short Answer Questions
SECTION A: Multiple Choice Questions (MCQs)
1. Thermodynamics mainly deals with the relationship between:
A) Mass and volume
B) Heat, work and energy
C) Pressure and density
D) Atomic structure
✅ Answer: B) Heat, work and energy
2. The part of the universe selected for study is called:
A) Surroundings
B) Boundary
C) System
D) Environment
✅ Answer: C) System
3. System and surroundings together form the:
A) Boundary
B) Universe
C) Atmosphere
D) Phase
✅ Answer: B) Universe
4. Which type of system can exchange both matter and energy with surroundings?
A) Closed system
B) Open system
C) Isolated system
D) Adiabatic system
✅ Answer: B) Open system
5. A thermos flask is an example of:
A) Open system
B) Closed system
C) Isolated system
D) Homogeneous system
✅ Answer: C) Isolated system
6. Which of the following is a state function?
A) Heat
B) Work
C) Internal energy
D) Path length
✅ Answer: C) Internal energy
7. The mathematical expression for the first law of thermodynamics is:
A) ΔH = ΔU + PV
B) ΔU = q + w
C) ΔG = ΔH + TS
D) PV = nRT
✅ Answer: B) ΔU = q + w
8. During expansion of a gas, work done by the system is:
A) Positive
B) Negative
C) Zero
D) Infinite
✅ Answer: B) Negative
9. During compression of a gas, work done is:
A) Negative
B) Positive
C) Zero
D) Undefined
✅ Answer: B) Positive
10. The equation for pressure-volume work is:
A) w = PV
B) w = -PΔV
C) w = q + ΔU
D) w = RT
✅ Answer: B) w = -PΔV
11. In free expansion of an ideal gas:
A) w = positive
B) w = negative
C) w = zero
D) q = positive
✅ Answer: C) w = zero
12. A process in which no heat exchange occurs is called:
A) Isothermal
B) Adiabatic
C) Reversible
D) Cyclic
✅ Answer: B) Adiabatic
13. Enthalpy is represented by:
A) U
B) H
C) S
D) G
✅ Answer: B) H
14. The relation between enthalpy and internal energy is:
A) H = U + PV
B) H = U − PV
C) H = PV/U
D) H = U/T
✅ Answer: A) H = U + PV
15. At constant pressure, heat change is equal to:
A) ΔU
B) ΔH
C) ΔG
D) ΔS
✅ Answer: B) ΔH
16. An exothermic reaction has:
A) ΔH positive
B) ΔH negative
C) ΔH zero
D) ΔS zero
✅ Answer: B) ΔH negative
17. An endothermic reaction absorbs:
A) Matter
B) Heat energy
C) Work only
D) Pressure
✅ Answer: B) Heat energy
18. Heat capacity is defined as heat required to raise temperature by:
A) 10 K
B) 5 K
C) 1 K
D) 100 K
✅ Answer: C) 1 K
19. The unit of molar heat capacity is:
A) J mol⁻¹ K⁻¹
B) J kg⁻¹
C) atm L
D) kJ mol
✅ Answer: A) J mol⁻¹ K⁻¹
20. For an ideal gas:
A) Cp = Cv
B) Cp < Cv
C) Cp > Cv
D) Cp = 0
✅ Answer: C) Cp > Cv
21. The relationship between Cp and Cv is:
A) Cp + Cv = R
B) Cp − Cv = R
C) Cp/Cv = R
D) Cp × Cv = R
✅ Answer: B) Cp − Cv = R
22. Bomb calorimeter measures:
A) ΔH
B) ΔU
C) ΔG
D) ΔS
✅ Answer: B) ΔU
23. Entropy is a measure of:
A) Heat
B) Pressure
C) Disorder
D) Volume
✅ Answer: C) Disorder
24. Entropy is highest in:
A) Solid
B) Liquid
C) Gas
D) Plasma only
✅ Answer: C) Gas
25. The formula for Gibbs free energy is:
A) ΔG = ΔH − TΔS
B) ΔG = ΔH + TΔS
C) ΔG = ΔU + PV
D) ΔG = q+w
✅ Answer: A) ΔG = ΔH − TΔS
26. A reaction is spontaneous when:
A) ΔG > 0
B) ΔG < 0
C) ΔG = 10
D) ΔH = 0
✅ Answer: B) ΔG < 0
27. At equilibrium:
A) ΔG = 0
B) ΔG < 0
C) ΔG > 0
D) ΔH = 0
✅ Answer: A) ΔG = 0
28. Hess’s law is based on the fact that enthalpy is a:
A) Path function
B) State function
C) Variable
D) Constant
✅ Answer: B) State function
29. Standard enthalpy of formation of an element in its stable form is:
A) 1
B) 100
C) Zero
D) Infinite
✅ Answer: C) Zero
30. The relation between Gibbs energy and equilibrium constant is:
A) ΔG° = RTlnK
B) ΔG° = −RTlnK
C) ΔG° = PV
D) ΔG° = q+w
✅ Answer: B) ΔG° = −RTlnK
SECTION B: Fill in the Blanks
- System and surroundings together form the ________.
✅ Answer: Universe
- Energy cannot be created or destroyed according to the law of ________.
✅ Answer: Conservation of energy
- The symbol used for internal energy is ________.
✅ Answer: U
- The first law is written as ________.
✅ Answer: ΔU = q + w
- Expansion work is generally ________.
✅ Answer: Negative
- Compression work is generally ________.
✅ Answer: Positive
- Enthalpy is represented by the symbol ________.
✅ Answer: H
- At constant pressure, heat absorbed is equal to ________.
✅ Answer: ΔH
- Entropy is represented by ________.
✅ Answer: S
- Gas has ________ entropy than solid.
✅ Answer: Higher
- A process with ΔG < 0 is called ________.
✅ Answer: Spontaneous
- A calorimeter is used to measure ________ changes.
✅ Answer: Heat
- Hess’s law states that total enthalpy change is the ________ of individual steps.
✅ Answer: Sum
- The SI unit of energy is ________.
✅ Answer: Joule
- Standard enthalpy is usually measured at ________ bar pressure.
✅ Answer: 1
SECTION C: True or False
- Heat and work are state functions.
❌ False
- Internal energy is a state function.
✅ True
- Open systems can exchange matter and energy.
✅ True
- An isolated system exchanges energy with surroundings.
❌ False
- Expansion of gas has negative work value.
✅ True
- Endothermic reactions have negative ΔH.
❌ False
- Entropy increases when solid changes into gas.
✅ True
- Gibbs free energy predicts spontaneity.
✅ True
- At equilibrium ΔG is zero.
✅ True
- Hess’s law applies because enthalpy depends on path.
❌ False
SECTION D: Very Short Answer Questions
1. What is thermodynamics?
Answer:
Thermodynamics is the study of heat, work and energy changes during physical and chemical processes.
2. Define system.
Answer:
The part of the universe selected for study is called the system.
3. Write the formula of enthalpy.
Answer:H=U+PV
4. What does negative ΔH indicate?
Answer:
It indicates an exothermic reaction.
5. What does positive ΔS indicate?
Answer:
It indicates an increase in disorder.
SECTION E: Assertion–Reason Questions
1. Assertion: Internal energy is a state function.
Reason: It depends only on initial and final states.
✅ Answer: Both assertion and reason are correct, and reason explains assertion.
2. Assertion: Expansion work is negative.
Reason: Energy leaves the system during expansion.
✅ Answer: Both are correct.
3. Assertion: A spontaneous reaction always occurs rapidly.
Reason: Spontaneity depends on Gibbs energy.
✅ Answer: Assertion is false, Reason is true.
4. Assertion: Entropy of gases is greater than solids.
Reason: Gas particles have more freedom of movement.
✅ Answer: Both are correct.
5. Assertion: Hess’s law can calculate unknown enthalpy changes.
Reason: Enthalpy is a state function.
✅ Answer: Both are correct.
SECTION F: Important Numerical Practice Questions
1. Calculate ΔU if q = 500 J and w = 200 J.
Formula:ΔU=q+w
Answer:ΔU=700J
2. A gas expands by 5 L against 2 atm pressure. Calculate work.
w=−PΔV w=−2×5 w=−10Latm
3. Calculate ΔG when:
ΔH = 100 kJ, T = 300 K, ΔS = 0.2 kJ/KΔG=ΔH−TΔS =100−(300×0.2) =40kJ
Reaction is non-spontaneous.