Chapter 19 - Equilibrium

Question 1

How do you calculate Kc?

Answer 1

[D]^d x [E]^e

[A]^a x [B] ^b

Question 2

How do you calculate the units for Kc?

Answer 2

Substitute units into the Kc expression, cancel common units and show the final answer on one line

Question 3

What are the two types of equilibria?

Answer 3

Homogeneous and heterogeneous equilibria

Question 4

What is a homogeneous equilibrium?

Answer 4

The equilibrium species all have the same state

Question 5

What is a heterogeneous equilibrium?

Answer 5

The equilibrium species can be in different states

Question 6

What is important to remember about calculating Kc for heterogeneous equilibria?

Answer 6

You don’t consider the concentrations of liquids or solids, just gases and those in the aqueous state

Question 7

What is Kp?

Answer 7

The equilibrium constant in terms of partial pressures

Question 8

What is the mole fraction of a gas?

Answer 8

The proportion by volume to the total volume of gas in a gaseous mixture

Question 9

How do you calculate a gas’ mole fraction?

Answer 9

Number of moles of A /

Total number of moles in the gaseous mixture

Question 10

What will the mole fractions of all the chemicals in equilibrium equal?

Answer 10

1

Question 11

What is the partial pressure of a gas?

Answer 11

The contribution that a gas makes towards the total pressure

Question 12

What will the partial pressures of all the chemicals in equilibrium equal?

Answer 12

The total pressure

Question 13

How do you calculate partial pressure?

Answer 13

Mole fraction of A x total pressure

Question 14

What species can be substituted into the Kp expression?

Answer 14

Gases only

Question 15

How do you calculate Kp?

Answer 15

p(C)^c x p(D)^d /

p(A)^a x p(B)^b

Question 16

What are suitable units for Kp?

Answer 16

Kilopascals (kPa) or atmospheres (atm)

Question 17

What does a K value of 1 mean?

Answer 17

Equilibrium is halfway between reactants and products

Question 18

What does a K value larger than 1 mean?

Answer 18

Equilibrium well in favour of products

Question 19

What does a K value less than 1 mean?

Answer 19

Equilibriums well in favour of reactants

Question 20

When will the value of K change?

Answer 20

If the temperature is changed

Question 21

If the forward reaction is exothermic, what happens when you increase the temperature?

Answer 21

Equilibrium will shift to the left and K will decrease

Question 22

What happens to the equilibrium constant if you change the pressure or concentration?

Answer 22

Nothing

Question 23

If the forward reaction is endothermic, what happens when you increase the temperature?

Answer 23

Equilibrium shifts to the right and K increases

Question 24

Explain why changing the concentration of one of the species at equilibrium shifts the position of equilibrium

Answer 24

You can use the le chateliers principle to predict shift as the Kc controls the relative concentrations of reactants and products present at equilibrium.

Question 25

How does a catalyst affect the equilibrium constant?

Answer 25

Has no effect on the position but the actual rate of the chemical reaction

Question 26

Explain why changing the pressure of one of the species at equilibrium changes the position of the equilibrium

Answer 26

If fewer moles of gaseous products the ratio < K (products to reactants) is increasing pressure, increases products whilst decreasing the reactants shifting the equilibrium to the right.

Question 27

Explain why increasing the temperature of an equilibrium where the forward reaction is endothermic will shift the equilibrium

Answer 27

F