SC12a Dynamic Equilibrium

Question 1

12.1 Recall that chemical reactions are reversible, the use of the symbol ⇌ in equations and that the direction of some reversible reactions can be altered by changing the reaction conditions​​

Question 2

12.3 Describe the formation of ammonia.

Question 3

12.4 State the conditions used for the Haber process.

Question 4

12.2 Explain what is meant by dynamic equilibrium.​

Question 5

12.5 Higher: Predict how the position of a dynamic equilibrium is affected by changes in:​

a) temperature​
b) pressure​
c) concentration​

Question 6

What is the haber process used for?

Answer 6

manufacture of ammonia

Question 7

what is ammonia used in?

Answer 7

fertilisers, explosives and some cleaning fluids

Question 8

what is used to manufacture ammonia?

Answer 8

nitrogen and hydrogen

Question 9

What is the reaction of the haber process?

Answer 9

N2 (g) + 3H2 (g) ⇌ 2NH3 (g)

Question 10

What is a reversible reaction?

Answer 10

when the reactants form the products and the products react to reform the reactants

Question 11

Use the equation for the haber process to explain what a reversible reaction is.

Answer 11

nitrogen reacts with hydrogen to form ammonia ammonia changes back into nitrogen and hydrogen

Question 12

what tells you if a reaction is reversible?

Answer 12

the double arrow between the reactants and the products

Question 13

What is dynamic equilibrium?

Answer 13

Dynamic equilibrium is when the forward and backward reactions are happening simultaneously at the same rate

Question 14

what is the example of a dynamic equilibrium reaction?

Answer 14

The Haber process

Question 15

Where does dynamic equilibrium occur

Answer 15

Any close system when no substances can enter all leave

Question 16

what changes the position of the equilibrium?

Answer 16

The reactions conditions

Question 17

how are the reaction conditions chosen?

Answer 17

to favour the fold reaction and make a large amount of the product as cheaply as possible

Question 18

What are the conditions used in the Haber process?

Answer 18

~450°c
~200 atmosphere pressure
~iron catalyst

Question 19

how does the equilibrium change when you increase the temperature?

Answer 19

~the equilibrium position shifts in the endothermic direction
~energy is transferred from the surroundings cooling them down the
~in the Haber process the equilibrium moves to the left

Question 20

How does the equilibrium change when you decrease the temperature?

Answer 20

the equilibrium position shifts in the exothermic direction
~energy transformed to the surroundings heating them up
~in the Haber process the equilibrium moves to the right

Question 21

the Haber process is usually run at 450°c, what would happen if the temperature increased?

Answer 21

The backwards reaction would be favoured as this is the endothermic reaction, this would reduce the temperature as the equilibrium moves to the left. A new mixture would contain less ammonia and more nitrogen and hydrogen

Question 22

What would happen to the equilibrium when you increase gas pressure?

Answer 22

~the equilibrium position will shift in the direction that forms fewer gas molecules, as this reduces pressure
~in the Haber process yet equilibrium moves to the right

Question 23

What would happen to the equilibrium when you decrease gas pressure?

Answer 23

~The equilibrium position will shift in a direction that forms more gas molecules, as this increases pressure
~in the Haber process the equilibrium moves to the left

Question 24

The Haber process is usually run at 200 atmospheres pressure, what would happen if the pressure was increased?

Answer 24

the forward reaction will be favoured as this is the direction which which forms fewer gas molecules, this would reduce the pressure as the equilibrium moves right, a new mixture would contain more ammonia than less nitrogen and hydrogen

Question 25

What would happen to the equilibrium when you increase the concentration?

Answer 25

The equilibrium position will shift in a direction that uses u[ the substance that has been added

Question 26

what would happen to the equilibrium when you decrease the concentration?

Answer 26

The equilibrium position will shift in the direction that forms more of the substance that has been removed

Question 27

What would happen if the concentration of ammonia increased?

Answer 27

the backwards reaction would be favoured as this would use up the substance that has been added, and would reduce the amount of ammonia as the equilibrium moves to the left the new mixture would contain less ammonia and more nitrogen on hydrogen

Question 28

Explain why the colour changes when the pressure is increased for this reversible reaction.
2NO2(g) — N2O4
brown — colourless

Answer 28

~if the pressure is increased the equilibrium position shifts in the direction which forms more N204
~as this decreases the pressure again
~when this happens the colour gets lighter less brown as N2O4 is colourless