Question 1

Which of the following statements best describes the law of conservation of energy?

Accepted Answer

The total energy in a system does not change; energy cannot be created or destroyed.

Question 2

A reaction has a $$	riangle H = -213$$ kcal/mol. Which of the following is true about this reaction?

Accepted Answer

It is exothermic and releases heat.

Question 3

Which bond has the highest bond dissociation energy and is therefore the strongest?

Accepted Answer

H–F

Question 4

If a chemical reaction requires more energy to break bonds than is released in forming new bonds, what is the sign of $$	riangle H$$ and what type of reaction is it?

Accepted Answer

$$	riangle H is $$positive; endothermic reaction

Question 5

Which of the following best describes the effect of a catalyst on a chemical reaction?

Accepted Answer

A catalyst lowers the activation energy ($$E_a) $$and increases the reaction rate.

Question 6

For the reaction $$2 	ext{CO}(g) + 	ext{O}_2(g) ightleftharpoons 2 	ext{CO}_2(g)$$, what happens if more $$	ext{CO}_2(g) is $$added?

Accepted Answer

The reaction shifts to the left, producing more $$	ext{CO}$$ and $$	ext{O}_2$$

Question 7

Which of the following is true for a reaction at equilibrium?

Accepted Answer

The rate of the forward reaction equals the rate of the reverse reaction.

Question 8

Given the reaction $$2 	ext{H}_2(g) + 	ext{O}_2(g) ightleftharpoons 2 	ext{H}_2	ext{O}(g)$$ with $$K = 2.9 	imes 10$$^{82}$$, what does the value of K$ indicate?

Accepted Answer

Equilibrium favors the products.

Question 9

Calculate the equilibrium constant $$K$$ for the reaction $$A_2$$ + $$B_2$$ ightleftharpoons 2 AB$$ given $$[$$A_2$$] = 0.25$$ M, $$[$$B_2$$] = 0.25$$ M, $$[AB] = 0.50$$ M.

Accepted Answer

$$K = 4.0$$

Question 10

Which scenario will increase the rate of a chemical reaction?

Accepted Answer

Adding a catalyst

Question 11

For the reaction $$N_2(g) + 3$$ $$H_2(g) $$ightleftharpoons 2 $$NH_3(g$$)$$, what happens if the pressure is increased?

Accepted Answer

Equilibrium shifts to the right, favoring $$NH_3$$

Question 12

Which of the following is a characteristic of an endothermic reaction?

Accepted Answer

Heat is absorbed and $$	riangle H is $$positive.

Question 13

What is the effect of increasing temperature on an exothermic reaction at equilibrium?

Accepted Answer

Equilibrium favors the reactants.

Question 14

Which of the following best describes the role of enzymes in the human body?

Accepted Answer

Enzymes lower the activation energy and speed up specific biological reactions.

Question 15

If the equilibrium constant $$K$$ for a reaction is much less than 1, what does this indicate?

Accepted Answer

Equilibrium favors the reactants.

Question 16

Which of the following is true about bond dissociation energy?

Accepted Answer

Bond dissociation energy is positive for breaking bonds.

Question 17

A reaction has a low activation energy ($$E_a). $$What does this imply about the reaction rate?

Accepted Answer

The reaction rate is fast.

Question 18

Which of the following changes will drive the equilibrium of $$C_2H_6O ightleftharpoons C_2H_4 + H_2O to $$the right?

Accepted Answer

Removing $$H_2O$$

Question 19

Which of the following is NOT a way to increase the rate of a chemical reaction?

Accepted Answer

Energy Changes, Reaction Rates, and Chemical Equilibrium6

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