Q: Consider the equilibrium: $$\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) + \text{Heat}. $$What will happen if the temperature is increased?

The equilibrium will shift to the left, producing more $$\text{N}_2$$ and $$\text{H}_2.$$

Q: For the reaction $$\text{CO}(g) + 2\text{H}_2(g) \rightleftharpoons \text{CH}_3\text{OH}(g)$$, which of the following is the correct expression for the equilibrium constant $$K$$?

$$K = \frac{[\text{CH}_3\text{OH}]}{[\text{CO}][\text{H}_2]^2}$$

Question 1

Which of the following best describes the difference between potential energy and kinetic energy in the context of chemical bonds?

Accepted Answer

Potential energy is stored in the attractive forces between atoms or ions, while kinetic energy is the energy of motion of particles.

Question 2

A reaction has a positive enthalpy change ($$\Delta H \u003e 0) $$and a positive entropy change ($$\Delta S \u003e 0). $$Under what condition will this reaction be spontaneous?

Accepted Answer

At high temperatures, because $$T\Delta S$$ can outweigh $$\Delta H.$$

Question 3

Which of the following statements about exothermic reactions is correct?

Accepted Answer

Exothermic reactions release heat to the surroundings and have a negative $$\Delta H.$$

Question 4

Given the reaction: $$2	ext{H}_2(g) + 	ext{O}_2(g) ightarrow 2	ext{H}_2	ext{O}(g)$$, and the following bond dissociation energies: $$	ext{H-H} = 103$$ kcal/mol, $$	ext{O=O} = 119$$ kcal/mol, $$	ext{O-H} = 112$$ kcal/mol, calculate $$\Delta H$$ for the reaction.

Accepted Answer

$$\Delta H = -123$$ kcal/mol

Question 5

Which of the following changes will increase the rate of a chemical reaction, according to collision theory?

Accepted Answer

Adding a catalyst to lower the activation energy.

Question 6

A reaction is described by the equation $$\Delta G = \Delta H - T\Delta S. If$$ $$\Delta H is $$negative and $$\Delta S is $$positive, what can be said about the spontaneity of the reaction?

Accepted Answer

The reaction is spontaneous at all temperatures.

Question 7

Which of the following best explains why increasing the concentration of reactants generally increases the rate of a reaction?

Accepted Answer

It increases the frequency of effective collisions between reactant molecules.

Question 8

Consider the equilibrium: $$	ext{N}_2(g) + 3	ext{H}_2(g) ightleftharpoons 2	ext{NH}_3(g) + 	ext{Heat}. $$What will happen if the temperature is increased?

Accepted Answer

The equilibrium will shift to the left, producing more $$	ext{N}_2$$ and $$	ext{H}_2.$$

Question 9

Which of the following is true about catalysts in chemical reactions?

Accepted Answer

Catalysts lower the activation energy and speed up the attainment of equilibrium.

Question 10

For the reaction $$	ext{CO}(g) + 2	ext{H}_2(g) ightleftharpoons 	ext{CH}_3	ext{OH}(g)$$, which of the following is the correct expression for the equilibrium constant $$K$$?

Accepted Answer

$$K = \frac{[	ext{CH}_3	ext{OH}]}{[	ext{CO}][	ext{H}_2]^2}$$

Question 11

Which of the following scenarios results in an increase in entropy ($$\Delta S \u003e 0$$)?

Accepted Answer

A solid dissolving in water to form an aqueous solution.

Question 12

A reaction has a large equilibrium constant ($$K \gg 1). $$What does this indicate about the reaction at equilibrium?

Accepted Answer

The reaction mixture contains mostly products.

Question 13

Which of the following changes will shift the equilibrium of the reaction $$	ext{N}_2(g) + 3	ext{H}_2(g) ightleftharpoons 2	ext{NH}_3(g) to $$the right?

Accepted Answer

Increasing the concentration of $$	ext{N}_2.$$

Question 14

Which of the following best describes the effect of increasing pressure on the equilibrium of a reaction involving gases?

Accepted Answer

It favors the side with fewer moles of gas.

Question 15

A chemical reaction has a high activation energy but a large negative $$\Delta G. $$What can be said about this reaction?

Accepted Answer

The reaction is thermodynamically favorable but may proceed slowly without a catalyst.

Question 16

Which of the following is a correct statement about reversible reactions at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions are equal.

Question 17

If the concentration of a product in a reversible reaction is continuously removed, what is the effect on the equilibrium?

Accepted Answer

The equilibrium shifts to produce more product.

Question 18

Which of the following is true regarding the law of conservation of energy in chemical reactions?

Accepted Answer

The total energy before and after a chemical reaction is the same.

Chapter 7: Chemical Reactions—Energy, Rates, and Equilibrium (GOB Chemistry Study Notes)

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