Q: A reaction has $$\Delta H = -100 kJ/$$mol and $$\Delta S = +200 J/($$mol\cdot K). At $$T = 298 K$$, what is $$\Delta G$$ for the reaction? (Note: 1 kJ = 1000 J)

$$\Delta G = -100,000 - (298 \times 200) = -159,600 J = -159.6$ kJ$$

Question 1

Which of the following statements best describes a spontaneous chemical reaction?

Accepted Answer

A reaction that, once started, proceeds without any external influence and releases free energy ($$\Delta G \u003c 0).$$

Question 2

Given the reaction: $$2NO(g) + O_2$(g) \rightarrow 2NO_2(g)$$, which of the following changes will increase the rate of reaction?

Accepted Answer

Adding a catalyst.

Question 3

Which equation correctly relates free energy change ($$\Delta G$$), enthalpy change ($$\Delta H$$), entropy change ($$\Delta S$$), and temperature ($$T$$)?

Accepted Answer

$$\Delta G = \Delta H - T\Delta S$$

Question 4

A reaction has $$\Delta H = -100 kJ/$$mol and $$\Delta S = +200 J/($$mol\cdot K). At $$T = 298 K$$, what is $$\Delta G$$ for the reaction? (Note: 1 kJ = 1000 J)

Accepted Answer

$$\Delta G = -100,000 - (298 	imes 200) = -159,600 J = -159.6$ kJ$$

Question 5

Which of the following will increase the entropy ($$\Delta S) of a $$system?

Accepted Answer

Dissolving a solid into water.

Question 6

For the reaction $$N_2(g) + 3H_2(g$$) \rightleftharpoons 2NH_3(g)$$, what will happen if the pressure is increased?

Accepted Answer

The equilibrium will shift toward the production of $$NH_3 ($$fewer moles of gas).

Question 7

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

It lowers the activation energy ($$E_a) $$and increases the reaction rate without being consumed.

Question 8

A reaction at equilibrium has $$K = 0.0005. $$Which statement is true?

Accepted Answer

There are more reactants than products at equilibrium.

Question 9

Which of the following changes will shift the equilibrium of an exothermic reaction to the left?

Accepted Answer

Increasing the temperature.

Question 10

If the activation energy ($$E_a) $$for a reaction is very high, what can be expected about the reaction rate?

Accepted Answer

The reaction rate will be very slow.

Question 11

Which of the following is true for a reaction with $$\Delta H  0 at $$all temperatures?

Accepted Answer

The reaction is spontaneous at all temperatures.

Question 12

Which of the following is NOT a factor that affects the rate of a chemical reaction?

Accepted Answer

The color of the reactants.

Question 13

For the reaction $$CO(g) + 2H_2(g) \rightleftharpoons CH_3OH(g)$$, what happens if more $$CO is $$added to the system at equilibrium?

Accepted Answer

The equilibrium shifts to the right, producing more $$CH_3OH.$$

Question 14

Which statement about chemical equilibrium is correct?

Accepted Answer

At equilibrium, the forward and reverse reaction rates are equal.

Question 15

A reaction has $$\Delta H = +50 kJ/$$mol and $$\Delta S = +150 J/($$mol\cdot K). At what temperature (in K) does the reaction become spontaneous?

Accepted Answer

$$T \u003e \frac{\Delta H}{\Delta S} = \frac{50,000}{150} = 333.3 K$$

Question 16

Which of the following is the best example of an increase in entropy?

Accepted Answer

Liquid water evaporating into vapor.

Question 17

Which of the following statements about the equilibrium constant $$K is $$correct?

Accepted Answer

If $$K \u003e 1$$, the forward reaction is favored and more products are present at equilibrium.

Question 18

Which of the following will NOT shift the position of equilibrium in a chemical reaction?

Accepted Answer

Adding a catalyst.

Question 19

Which of the following is true for an endothermic reaction?

Accepted Answer

Heat is a reactant and $$\Delta H is $$positive.

Chap 7: Energy, Rates, and Equilibrium: Study Notes for GOB Chemistry

Study Guide - Practice Questions

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