Chapter 19

Question 1

What happens when the KC value gets larger?

Answer 1

The position of equilibrium lies further to the RHS

Question 2

How did you show the units?

Answer 2

On a single line

Question 3

What is a homogeneous equilibrium?

Answer 3

It’s an equilibrium which contains proceed with the same state of phase e.g all gaseous, all liquids all aqueous.

Question 4

What is a heterogeneous equilibrium?

Answer 4

It’s an equilibrium which contains species that have different states.

Question 5

Which species can be included in the KC expression for a homogeneous equilibrium?

Answer 5

All species can be included in the expression.

Question 6

Which species can be included in the KC expression in a heterogeneous equilibrium?

Answer 6

Only the aqueous and gaseous species are included. Solids and pure liquids are omitted as they remain constant.

Question 7

How do you workout equilibrium quantities and KC?

Answer 7

1. Use the equation to work out the equilibrium amounts of all species.
2. Convert into concentration using the total volume of the container (the volume should be in dm3)
3. Write Kc and sub in values, to calculate

Question 8

What is KP?

Answer 8

It’s an equilibrium which involves gases it’s an expressed in terms KP equilibrium constant in terms of partial pressures. Concentration and pressure of proportional to another and KP has a direct relationship with KC

Question 9

What is an mole fraction

Answer 9

Under the same conditions of temperature and pressure the same volume of different gases contains the same number of moles of gas molecules. The mole fraction of the gas is the same as its proportional by volume to total volume of gases in the gas mixture.

Question 10

How do you workout mole fraction?

Answer 10

N.o of moles of A/ total n.o of moles in a gas mixture

Question 11

What does the sum of the mole fractions add up to?

Answer 11

1

Question 12

What is the partial pressure of a gas?

Answer 12

The contribution that the gas makes towards the total pressure of a gas mixture.

Question 13

What is the sum of partial pressures of each gas equal to?

Answer 13

Total pressure

Question 14

How do you calculate partial pressure, p(A)?

Answer 14

Mole fraction (A) x total pressure, P

Question 15

What are suitable units?

Answer 15

kPa, Pa, atm

Question 16

For Kp which species are included in a heterogeneous equilibrium ?

Answer 16

Only gaseous species

Question 17

How do you work out KP?

Answer 17

1. Find the mole fraction
2. Find the partial pressure
3. Calculate Kp

Question 18

Define Le Chatelier’s principle?

Answer 18

When a system in equilibrium is subjected to an external change the system readjust itself to minimise the effect of that change.

Question 19

What happens when the concentration increases?

Answer 19

The position of equilibrium shifts in the direction that reduces concentration.

Question 20

What happens to equilibrium when total pressure is increased

Answer 20

The position shifts to the side with fewer gaseous moles.

Question 21

What happens to equilibrium when the temperature is increased?

Answer 21

Position shifts in the endothermic direction

Question 22

What happens when a catalyst is added?

Answer 22

The rate at which equilibrium is established increases.

Question 23

What does it indicate when K=1?

Answer 23

Equilibrium is halfway between reactants and products

Question 24

What does it indicate when K=100?

Answer 24

Equilibrium is in favour of the products

Question 25

What does it indicate when K=1x10-2?

Answer 25

Equilibrium is in favour of the reactants

Question 26

What does K indicate?

Answer 26

Exact position of equilibrium. When in a reversible reaction the reaction proceeds until the concentration of the species gives K when in the KC expression.

Question 27

What will not change the value of KC/KP?

Answer 27

Changing the concentration, pressure or adding a catalyst.

Question 28

When will the equilibrium constant change?

Answer 28

If temperature is changed

Question 29

What happens in an exothermic reaction?

Answer 29

If the forward reaction is exothermic the equilibrium constant decreases with increasing temperature. Raising the temperature decreases the product yield. The position shifts to the left. THE CONSTANT DECREASES WITH INCREASING TEMPERATURE.

Question 30

What happens when the ratio is greater than KP?

Answer 30

The partial pressure of the numerator must decrease and the partial pressure of the denominator must increase. Position shift to the left. A new equilibrium will be reached when the KP value is equal to the expression.

Question 31

What happens in an endothermic reaction?

Answer 31

When the forward reaction is endothermic equilibrium constant increases with increasing temperature. Raising the temperature increases the product yield. THE CONSTANT INCREASES WITH INCREASING TEMPERATURE.

Question 32

What happens when the expression is less than KP?

Answer 32

The numerator value must increase and the denominator value must decrease.

Question 33

What happens if there is an increase in concentration of products?

Answer 33

The numerator will increase. The expression (NOT Kc) will have a value greater than Kc. To restore the expression to Casey the numerator will have to decrease and the denominator will increase. Hence the concentration of reactants increasing and the products concentration decreasing.

Question 34

What happens when there are fewer moles of gaseous products?

Answer 34

ratio < k increasing pressure - products increase, reactants decrease equilibrium shifts to the right

Question 35

What happens when there are more moles of gaseous products?

Answer 35

ratio > k increasing pressure - products decrease, reactants increase equilibrium shifts to the left

Question 36

What happens when there are same number of gaseous moles?

Answer 36

ratio = k increasing pressure - no change no effect to the equilibrium

Question 37

What happens to the equilibrium constant when a catalyst is added?

Answer 37

Equilibrium constants ARE NOT affected by catalysts. It affects the rate but not the position, it speeds up the forward and reverse reactions in the equilibrium by the same factor so equilibrium is reached faster.