Chapter 19 - Equilibrium

Question 1

How are the units of Kc worked out?

Answer 1

Substitute units into the expression

Cancel common units

Question 2

What is a homogeneous equilibrium?

Answer 2

in homogeneous equilibrium all Equilibrium species all have the same state.

N2(g) + 3H2 (g) = 2NH3 (g)

all species in this example are gas

Question 3

What is a heterogeneous equilibrium?

Answer 3

In heterogeneous equilibrium Equilibrium species that have different states.

C(s) + H2O (g) = CO(g) + H2(g)

Question 4

In a heterogeneous equilibrium, what is discounted in the expression for Kc?

Answer 4

Any species that are not a gas or in solution (aqueous) .

so solids and liquids are ommited

Question 5

What is a mole fraction?

Answer 5

The proportion of the volume of a gas to the total volume of gases in the mixture.

Question 6

What is the partial pressure?

Answer 6

The contribution that the gas makes towards the total pressure P.

Question 7

mole fraction equation?

Answer 7

Mole fraction χ(A) = n(A)/n(total)

Question 8

How is partial pressure calculated?

Answer 8

p(A) = mole fraction x total pressure P
p(A) = χ(A) x P

Question 9

What is the way to check the partial pressures are correct?

Answer 9

Sum of the partial pressures equals the total pressure.

Question 10

what is Kp?

Answer 10

Kp is the equilibrium constant using gases.

Question 11

With the equilibrium H(2) + I(2) = 2HI, what is the expression for Kp?

Answer 11

Kp = p(HI)^2 / p(H(2)) x p(I(2))

Question 12

What does the magnitude of an equilibrium constant represent?

Answer 12

The extent of an equilibrium

Question 13

What would K=1, K=100 and K=0.01 represent?

Answer 13

K=1: equilibrium halfway between reactants and products
K=100: equilibrium in favour of products
K=0.01: equilibrium in favour of reactants

Question 14

What is the effect on K when the temperature is increased and the forward reaction is exothermic?

Answer 14

Equilibrium constant decreases

Equilibrium shifts to reactant side

Question 15

What is the effect on K when the temperature is increased and the forward reaction is endothermic?

Answer 15

Equilibrium constant increases

Equilibrium shifts to product side

Question 16

What effect does increasing pressure have on a reaction with fewer moles of gaseous products than reactants?

Answer 16

Products increase
so Reactants decrease
so Equilibrium shifts to left

Question 17

What effect does increasing pressure have on a reaction with more moles of gaseous products than reactants?

Answer 17

Products decrease
Reactants increase
Equilibrium shifts to left

Question 18

What effect does increasing pressure have on a reaction with the same number of moles of gaseous products and reactants?

Answer 18

No change

Equilibrium stays the same

Question 19

What is the effect of a catalyst on the equilibrium constant?

Answer 19

Catalysts affect the rate but not the equilibrium position.

Equilibrium is reached faster but position does not change.