5.1.2 How far?

Question 1

Define Le Chatelier’s principle

Answer 1

If a system at equilibrium is disturbed by a change in conditions, the position of equilibrium moves in the direction that counteracts the change

Question 2

Define homogeneous equilibria

Answer 2

All species are in the same state

Question 3

Define heterogeneous equilibria

Answer 3

Species are in different states

Question 4

How do you write an expression for equilibrium constant?

Answer 4

Kc = [products ( )] ^mole / [reactants ( )] ^mole

Question 5

What is the unit used in equilibrium constant?

Answer 5

moldm-3

Question 6

What does a higher Kc mean?

Answer 6

Equilibrium lies to the right

Question 7

How do you work out Kc using ICE?

Answer 7

Initial amount (mol) - one side starts with moles proportional to each other and the other side starts at 0 mol
Change - add or subtract moles based on moles at equilibrium. should be proportional to moles
Equilibrium amount (mol)
Equilibrium concentration (moldm-3) - calculated using moles/volume.
Use the Kc expression to sub concentrations in

Question 8

Which factor affects the value of equilibrium constant?

Answer 8

Temperature

Question 9

How does increasing the temperature affect Kc, assuming the forward reaction is endothermic?

Answer 9

Shifts equilibrium to the endothermic direction to the right towards the products. This increases the yield and therefore the value of Kc

Question 10

How does decreasing the temperature affect Kc, assuming the forward reaction is endothermic?

Answer 10

Shifts equilibrium to the exothermic direction to the left towards the reactants. This decreases the yield and therefore the value of Kc

Question 11

Does pressure affect the value of Kc?

Answer 11

No

Question 12

How do you calculate mole fraction?

Answer 12

Equilibrium moles of one component/ total moles of all components

Question 13

How do you calculate partial pressure?

Answer 13

Mole fraction of the gas x total pressure of the mixture

Question 14

What is the sum of the partial pressures?

Answer 14

The total pressure of the mixture of gases

Question 15

What are the units of pressure?

Answer 15

Pa

Question 16

How is Kp calculated?

Answer 16

Use the ICE method to find equilibrium moles.
Calculate the mole fraction by dividing equilibrium moles by total moles.
Calculate partial pressure by multiplying mole fraction by total pressure.
Sub into expression for Kp

Question 17

How do you write an expression for Kp?

Answer 17

Kp = [p products (g)] ^moles / [p reactants (g)] ^moles

Question 18

What factor affects Kp?

Answer 18

Temperature

Question 19

How does decreasing the temperature affect Kp, assuming the forward reaction is exothermic?

Answer 19

Kp increases with a decrease in temperature.
Shifts equilibrium in the exothermic direction to the right towards the product.
Yield increases

Question 20

How does increasing the temperature affect Kp, assuming the forward reaction is exothermic?

Answer 20

Kp decreases with an increase in temperature.
Shifts equilibrium in the endothermic direction to the left towards the reactants.
Yield decreases

Question 21

Define partial pressure

Answer 21

The pressure due to each gas alone in a mixture

Question 22

Kp expressions only involve what state of species and why?

Answer 22

Gaseous species because solid species do not have a gas pressure (omitted)

Question 23

How do catalysts affect equilibrium position?

Answer 23

Remains unchanged. Forward and reverse reaction are affects by the same amount and equilibrium is reached in less time