Chapter Exam

Chapter 8: Physical and Chemical Equilibrium — Online MCQ Test

Q: What is the relationship between Kp and Kc for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g)?

Answer: A. Kp = Kc(RT)^-2 — For this reaction, Δn = 2 - 4 = -2. Using Kp = Kc(RT)^Δn, we get Kp = Kc(RT)^-2.

Q: For a reaction to be spontaneous at all temperatures, the values of ΔH and ΔS must be:

Answer: A. ΔH 0 — According to the Gibbs-Helmholtz equation ΔG = ΔH - TΔS, spontaneity requires ΔG < 0, which occurs when ΔH is negative and ΔS is positive.

Q: Consider the system A(g) + B(g) ⇌ C(g) + D(g). If the volume of the container is increased, what happens to the equilibrium?

Answer: C. It does not shift as the number of moles is equal on both sides. — Since the total number of moles of gas is equal on both sides (2=2), changing the volume/pressure has no effect on the equilibrium position.

Q: Which statement correctly describes the effect of a catalyst on an equilibrium system?

Answer: B. It lowers the activation energy of both forward and backward reactions equally. — A catalyst provides an alternative pathway with lower activation energy, speeding up both reactions equally without changing the equilibrium state.

CHEMISTRY · CLASS 11th · Tamil Nadu State Board

Practice Chapter 8: Physical and Chemical Equilibrium with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 11th CHEMISTRY. This chapter covers: This chapter examines reversible reactions law of mass action equilibrium constants Kc and Kp. Students explore Le Chatelier principle factors affecting equilibrium phase equilibri.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 8: Physical and Chemical Equilibrium — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 11th CHEMISTRY — Chapter 8: Physical and Chemical Equilibrium, with answers and explanations. These are sample questions; the exam has its own separate question set.

Which of the following is a characteristic of a chemical system at equilibrium?

A. The concentrations of reactants and products are equal.
B. The rates of forward and backward reactions are equal. ✓
C. The reaction stops completely.
D. The system reaches a state of minimum entropy.

Answer: B. The rates of forward and backward reactions are equal.
At equilibrium, the dynamic nature of the reaction ensures that the rate of the forward reaction equals the rate of the backward reaction.

What is the relationship between Kp and Kc for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g)?

A. Kp = Kc(RT)^-2 ✓
B. Kp = Kc(RT)^2
C. Kp = Kc(RT)^-1
D. Kp = Kc

Answer: A. Kp = Kc(RT)^-2
For this reaction, Δn = 2 - 4 = -2. Using Kp = Kc(RT)^Δn, we get Kp = Kc(RT)^-2.

For a reaction to be spontaneous at all temperatures, the values of ΔH and ΔS must be:

A. ΔH < 0 and ΔS > 0 ✓
B. ΔH > 0 and ΔS > 0
C. ΔH < 0 and ΔS < 0
D. ΔH > 0 and ΔS < 0

Answer: A. ΔH < 0 and ΔS > 0
According to the Gibbs-Helmholtz equation ΔG = ΔH - TΔS, spontaneity requires ΔG < 0, which occurs when ΔH is negative and ΔS is positive.

Consider the system A(g) + B(g) ⇌ C(g) + D(g). If the volume of the container is increased, what happens to the equilibrium?

A. It shifts to the side with more moles.
B. It shifts to the side with fewer moles.
C. It does not shift as the number of moles is equal on both sides. ✓
D. It shifts towards the product side.

Answer: C. It does not shift as the number of moles is equal on both sides.
Since the total number of moles of gas is equal on both sides (2=2), changing the volume/pressure has no effect on the equilibrium position.

Which statement correctly describes the effect of a catalyst on an equilibrium system?

A. It shifts the equilibrium to the right, increasing product yield.
B. It lowers the activation energy of both forward and backward reactions equally. ✓
C. It increases the value of Kc.
D. It decreases the rate of the reverse reaction to favor the forward reaction.

Answer: B. It lowers the activation energy of both forward and backward reactions equally.
A catalyst provides an alternative pathway with lower activation energy, speeding up both reactions equally without changing the equilibrium state.

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