Equilibrium 2 - Kp

Question 1

If a reaction under equilibrium contains gases…

Answer 1

Then an alternative reaction can be set up using the partial pressures of gases instead of concentrations

Question 2

Partial pressure of a gas is…

Answer 2

The pressure of a single gas (that’s in a mixture) that the gas would exert if it occupied the same volume as the gaseous mixture

Question 3

What is the total gas mixtures pressure?

Answer 3

Every gas in the mixture’s partial pressure
Added together

Question 4

What is Kp?

Answer 4

An equilibrium constant that uses partial pressures in the expression instead of concentrations
So can tell us the position of equilibrium

Question 5

What do equilibrium constants (Kp, Kc) tell us?

Answer 5

The ratio of products to reactants at equilibrium, thus how far to the right or left the position of equilibrium is

Question 6

How do we write an expression for Kp?

Answer 6

partial pressure of products
——————————————— = Kp
partial pressure of reactants

Question 7

How do we represent the partial pressures in the expression for Kp?

Answer 7

NO SQUARE BRACKETS
p (gas formula)
To the power of the stoichiometry

Question 8

Units for Kp

Answer 8

Substitute in the units for each partial pressure into the Kp expression and work out the units by cancelling/multiplying

Question 9

The mole fraction

Answer 9

The number of moles of a gas
————————————————
Total number of moles of all gases

Question 10

What does the mole fraction show?

Answer 10

The percentage of how much of one gas we have in a mixture out of the total amount of gas in the mixture

Question 11

How to find the partial pressure of a gas from the mole fraction?

Answer 11

Multiply the specific gas’s mole fraction by the total pressure of gas
To find partial pressure

Question 12

If given a percentage instead of mole fraction…

Answer 12

The percentage shows the percent of that gas in the gas mixture so we can work out the partial pressure by multiplying partial pressure by total pressure of gas
Then take away this partial pressure from total pressure to find the pressures of unknown gases
And we can share this value in the ratio depending on their stoichiometry

Question 13

What changes the value of Kp?

Answer 13

Only temperature

Question 14

The value of Kp stays constant at…

Answer 14

1 temperature

Question 15

If you increase the temperature…

Answer 15

The pressures of products of the endothermic reaction increases
The pressures of reactants of exothermic reaction decrease
To overcome the change in equilibrium by taking heat energy in, POE shifts to favour endothermic reaction

Question 16

If you decrease the temperature…

Answer 16

The pressures of products of the exothermic reaction increase
The pressures of products of endothermic reaction decrease
Because POE shifts to favour exothermic reaction to oppose the decrease in heat energy so heat energy released

Question 17

What factors don’t change the Kp value?

Answer 17

Pressure
Catalysts

Question 18

How does changing pressure affect value of Kp?

Answer 18

Has no affect because
The position of equilibrium will shift in order to keep the ratios of partial pressures of reactants to gases the same for each given temperature. So Kp stays constant

Question 19

How do catalysts affect the value of Kp?

Answer 19

No affect because…
The ratio of partial pressures of reactants to gases stays the same (Kc value constant) at this temp
But rate of reaction increases equally for both forward and backward reaction, the pressures remain same but equilibrium achieved quicker