Chapter Exam

Chapter 5: Chemical Thermodynamics — Online MCQ Test

Q: Which of the following best defines a thermodynamic system?

Answer: A. The portion of the universe selected for study — A thermodynamic system is the part of the universe chosen for study. Everything outside it is called the surroundings.

Q: Which type of system can exchange both matter and energy with its surroundings?

Answer: A. Open system — An open system allows exchange of both matter and energy with the surroundings.

Q: If a system absorbs heat from the surroundings, the sign of q is:

Answer: B. positive — Heat absorbed by the system is taken as positive.

Q: For a process with ΔH = -50 kJ and ΔS = -0.10 kJ K⁻¹ at 300 K, the sign of ΔG is:

Answer: B. negative — Using ΔG = ΔH - TΔS = -50 - 300(-0.10) = -20 kJ, so ΔG is negative.

Q: For a reaction, if ΔH = +80 kJ mol⁻¹ and ΔS = +200 J K⁻¹ mol⁻¹, the temperature above which the reaction becomes spontaneous is:

Answer: B. 800 K — Spontaneity requires ΔG ΔH/ΔS = 80,000/200 = 400 K. Among the options, 400 K is the threshold, so spontaneity begins above it.

CHEMISTRY · CLASS 11 FIRST PUC · Karnataka State Board

Practice Chapter 5: Chemical Thermodynamics with a free chapter-wise online MCQ test for Karnataka State Board CLASS 11 FIRST PUC CHEMISTRY. This chapter covers: System Surroundings Enthalpy Entropy Gibbs free energy Heat Work Internal energy Hess law Spontaneous process. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 5: Chemical Thermodynamics — Important Questions & Answers (FAQ)

Frequently asked questions from Karnataka State Board CLASS 11 FIRST PUC CHEMISTRY — Chapter 5: Chemical Thermodynamics, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following best defines a thermodynamic system?

A. The portion of the universe selected for study ✓
B. The entire universe excluding surroundings
C. Only the container used in an experiment
D. Only the reactants in a chemical reaction

Answer: A. The portion of the universe selected for study
A thermodynamic system is the part of the universe chosen for study. Everything outside it is called the surroundings.

Which type of system can exchange both matter and energy with its surroundings?

A. Open system ✓
B. Closed system
C. Isolated system
D. Adiabatic system

Answer: A. Open system
An open system allows exchange of both matter and energy with the surroundings.

If a system absorbs heat from the surroundings, the sign of q is:

A. negative
B. positive ✓
C. zero
D. cannot be determined

Answer: B. positive
Heat absorbed by the system is taken as positive.

For a process with ΔH = -50 kJ and ΔS = -0.10 kJ K⁻¹ at 300 K, the sign of ΔG is:

A. positive
B. negative ✓
C. zero
D. cannot be determined

Answer: B. negative
Using ΔG = ΔH - TΔS = -50 - 300(-0.10) = -20 kJ, so ΔG is negative.

For a reaction, if ΔH = +80 kJ mol⁻¹ and ΔS = +200 J K⁻¹ mol⁻¹, the temperature above which the reaction becomes spontaneous is:

A. 400 K
B. 800 K ✓
C. 1200 K
D. 1600 K

Answer: B. 800 K
Spontaneity requires ΔG < 0, so T > ΔH/ΔS = 80,000/200 = 400 K. Among the options, 400 K is the threshold, so spontaneity begins above it.