Gen Chem Final Exam

Question 1

How can the value of Kc be calculated?

Answer 1

Using the equilibrium concentrations of reactants and products.

Question 2

What does a small Kc value distinguish?

Answer 2

More reactants than products.
- little reaction takes place

Question 3

What does a large Kc value distinguish?

Answer 3

More products than reactants
- reaction is essentially complete

Question 4

What does it mean when the Kc = 1?

Answer 4

Reactants = Products
- moderate reaction

Question 5

What does the size of the equilibrium constant not affect?

Answer 5

How fast the equilibrium is reached.

Question 6

Reaction Quotient (Qc)

Answer 6

Qc = [products]/[reactants]
- same as Kc

Question 7

What happens if Qc=Kc?

Answer 7

-Reactant and product concentrations are equilibrium concentrations

-Reaction mixture is at equilibrium

Question 8

What happens if Qc≠Kc?

Answer 8

-Reactant concentrations are NOT equilibrium concentrations

-Reaction mixture is NOT at equilibrium

Question 9

Le Chatelier’s Principle

Answer 9

When a stress (a change) is placed on a reaction at equilibrium.

Question 10

How does the system respond to stress (changes)?

Answer 10

Momentarily changing the rate of the forward/reverse reaction in the direction.

= Relieves that stress until the equilibrium is re-established

Question 11

What happens to the rate of reaction when more reactant is added?

Answer 11

Rate of forward reaction increases to form more products until the system re-establishes equilibrium.

Question 12

What happens to the equilibrium when more reactants are added?

Answer 12

The equilibrium shifts toward the products (forward direction)

Question 13

What happens to the rate of reaction when reactant is removed?

Answer 13

Rate of the reverse reaction increases to form more reactant until the system re-establishes the equilibrium.

Question 14

What happens to the equilibrium when reactants are removed?

Answer 14

The equilibrium shifts toward the reactants (reverse direction)

Question 15

What happens to the rate of reaction when more product is added?

Answer 15

Rate of the reverse reaction increases to consume the product until the system re-establishes the equilibrium

Question 16

What happens to the equilibrium when more products are added?

Answer 16

The equilibrium shifts toward the reactants (reverse direction)

Question 17

What happens to the rate of reaction when product is removed?

Answer 17

The rate of the forward reaction increases to form more products until the system re-establishes equilibrium.

Question 18

What happens to the equilibrium when products are removed?

Answer 18

The equilibrium shifts toward the products (forward direction).

Question 19

What does changing the volume of a gas mixture at equilibrium cause?

Answer 19

Change in the concentration of gases in the mixture

Question 20

What happens to the pressure of a mixture when the volume is decreased?

Answer 20

The pressure increases

Question 21

What happens to the concentration of a mixture when the volume is decreased?

Answer 21

The concentration increases

Question 22

What happens to the equilibrium when the volume is decreased?

Answer 22

The equilibrium shifts in the direction of the smaller number of moles to compensate.

Question 23

What happens to the pressure of a mixture when the volume is increased?

Answer 23

The pressure decreases

Question 24

What happens to the concentration of a mixture when the volume is increased?

Answer 24

The concentration decreases

Question 25

What happens to the equilibrium when the volume is increased?

Answer 25

The equilibrium shifts in the direction of the larger number of moles to compensate.

Question 26

What effect does volume/pressure change have on a reaction with the same amount of reactants and products?

Answer 26

NO EFFECT

Question 27

What happens to the rate of reaction when temperature is increased in ENDOTHERMIC reactions?

Answer 27

The rate of the forward reaction increases to consume the added heat energy until the system re-establishes equilibrium.

Question 28

What happens to the equilibrium when temperature is increased in ENDOTHERMIC reactions?

Answer 28

The equilibrium shifts toward the products (forward direction)

Question 29

What happens to the rate of reaction when temperature is decreased in ENDOTHERMIC reactions?

Answer 29

The rate of the reverse reaction increases to generate more heat energy until the system re-establishes the equilibrium.

Question 30

What happens to the equilibrium when temperature is decreased in ENDOTHERMIC reactions?

Answer 30

The equilibrium shifts toward the reactants (reverse direction).

Question 31

What happens to the rate of reaction when temperature is increased in EXOTHERMIC reactions?

Answer 31

The rate of the reverse reaction increases to consume the added heat energy until the system re-establishes the equilibrium.

Question 32

What happens to the equilibrium when temperature is increased in EXOTHERMIC reactions?

Answer 32

The equilibrium shifts toward the reactants (reverse direction).

Question 33

What happens to the rate of reaction when temperature is decreased in EXOTHERMIC reactions?

Answer 33

The rate of the forward reaction increases to generate more heat until the system re-establishes the equilibrium.

Question 34

What happens to the equilibrium when temperature is decreased in EXOTHERMIC reactions?

Answer 34

The equilibrium shifts toward the products (forward direction)

Question 35

How does the addition of a catalyst affect the rate of reaction?

Answer 35

Speeds up a reaction by lowering the activation energy, which increases the rate of the forward and reverse reactions equally.

Question 36

Are the ratios of reactants and products changed when a catalyst is added?

Answer 36

No; only the time to reach equilibrium is shorter

Question 37

Does the addition of a catalyst shift the equilibrium?

Answer 37

No