Chapter 7: Thermodynamics — Online MCQ Test
CHEMISTRY · CLASS 11th · Tamil Nadu State Board
Practice Chapter 7: Thermodynamics with a free chapter-wise online MCQ test.
This chapter covers: Focusing on chemical energetics this chapter covers system types state functions first second and third laws of thermodynamics. Students calculate enthalpy changes Hess law applica....
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Chapter 7: Thermodynamics — Important Questions & Answers
Which one of the following is an example of an open system?
- A. A sealed steel bomb calorimeter
- B. Boiling water in an open beaker
- C. Gas enclosed in a rigid container
- D. Ice kept in a closed flask
Answer: B. Boiling water in an open beaker
An open system can exchange both matter and energy with the surroundings. Boiling water in an open beaker loses water vapour and exchanges heat with the surroundings.
An open system can exchange both matter and energy with the surroundings. Boiling water in an open beaker loses water vapour and exchanges heat with the surroundings.
Which of the following is a state function?
- A. Heat
- B. Work
- C. Internal energy
- D. Path length
Answer: C. Internal energy
Internal energy depends only on the initial and final states of the system, not on the path followed. Heat and work are path functions.
Internal energy depends only on the initial and final states of the system, not on the path followed. Heat and work are path functions.
If a system absorbs 200 J of heat and does 50 J of work on the surroundings, what is the change in internal energy?
- A. 150 J
- B. 250 J
- C. -150 J
- D. -250 J
Answer: A. 150 J
Using ΔU = q + w, heat absorbed is +200 J and work done by the system is -50 J. Therefore, ΔU = 200 + (−50) = 150 J.
Using ΔU = q + w, heat absorbed is +200 J and work done by the system is -50 J. Therefore, ΔU = 200 + (−50) = 150 J.
A reaction has ΔH = -40 kJ mol⁻¹ and ΔS = -100 J mol⁻¹ K⁻¹. At 300 K, which is correct for ΔG?
- A. ΔG is negative and reaction is spontaneous
- B. ΔG is positive and reaction is non-spontaneous
- C. ΔG is zero and reaction is at equilibrium
- D. ΔG cannot be calculated
Answer: A. ΔG is negative and reaction is spontaneous
Convert ΔS to kJ: -100 J mol⁻¹ K⁻¹ = -0.100 kJ mol⁻¹ K⁻¹. Then ΔG = ΔH - TΔS = -40 - 300(−0.100) = -10 kJ mol⁻¹, so it is spontaneous.
Convert ΔS to kJ: -100 J mol⁻¹ K⁻¹ = -0.100 kJ mol⁻¹ K⁻¹. Then ΔG = ΔH - TΔS = -40 - 300(−0.100) = -10 kJ mol⁻¹, so it is spontaneous.
Which statement is correct for a reversible isothermal expansion of an ideal gas?
- A. ΔU is always positive
- B. ΔU = 0
- C. q = 0
- D. w = 0
Answer: B. ΔU = 0
For an ideal gas, internal energy depends only on temperature. In an isothermal process, temperature remains constant, so ΔU = 0.
For an ideal gas, internal energy depends only on temperature. In an isothermal process, temperature remains constant, so ΔU = 0.