M5 - Equilibrium (how far?)

Question 1

Answer 1

B

Question 2

what is Kp?

Answer 2

Kp is the equilibrium constant using gases.

Question 3

How is partial pressure calculated?

Answer 3

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

Question 4

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

Answer 4

No change

Equilibrium stays the same

Question 5

What is a homogeneous equilibrium?

Answer 5

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 6

Answer 6

B

Question 7

Answer 7

B

Question 8

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

Answer 8

Catalysts affect the rate but not the equilibrium position.

Equilibrium is reached faster but position does not change.

Question 9

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

Answer 9

Products increase
so Reactants decrease
so Equilibrium shifts to right

Question 10

What is the formula to calculate the partial pressure for gas equilibria? (1)

Answer 10

Partial Pressure p(A) = mole fraction of A x total pressure P (1)

Question 11

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

Answer 11

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

Question 12

Write a Kp expression for this equilibrium reaction

Answer 12

Question 13

What does the magnitude of an equilibrium constant represent?

Answer 13

The extent of an equilibrium

Question 14

What is a heterogeneous equilibrium?

Answer 14

In heterogeneous equilibrium Equilibrium species that have different states.

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

Question 15

Answer 15

Question 16

Write a Kc expression for this equilibrium reaction

Answer 16

Question 17

What is the formula to calculate the mole fraction for gas equilibria? (1)

Answer 17

Mole fraction x(A) = number of moles of A / total number of moles in a gas mixture (1)

Question 18

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

Answer 18

Sum of the partial pressures equals the total pressure.

Question 19

What is the partial pressure?

Answer 19

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

Question 20

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

Answer 20

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

so solids and liquids are ommited

Question 21

What is a mole fraction?

Answer 21

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

Question 22

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

Answer 22

Products decrease
Reactants increase
Equilibrium shifts to left

Question 23

Answer 23

D

Question 24

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

Answer 24

Equilibrium constant increases

Equilibrium shifts to product side

Question 25

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

Answer 25

Equilibrium constant decreases

Equilibrium shifts to reactant side

Question 26

mole fraction equation?

Answer 26

Mole fraction χ(A) = n(A)/n(total)

Question 27

Answer 27

B

Question 28

How are the units of Kc worked out?

Answer 28

Substitute units into the expression

Cancel common units

Question 29

Answer 29

B

Question 30

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

Answer 30

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