Equilibrium

Question 1

What is the definition of dynamic equilibrium ? (2 marks)

Answer 1

1) concentrations of reactants and products remain constant
2) the rate of the forward = rate of the reverse reaction

Question 2

Describe how is dynamic equilibrium reached ?

Answer 2

1) start ; forward = fast, backward = slow
2) backward speeds up as forward slows down
3) rate of forward reaction becomes the same as the rate of the backward reaction

Question 3

State a condition for a reaction in equilibrium ( 1 mark)

Answer 3

Closed system

Question 4

State Le Chateliers principle

Answer 4

position of equilibrium will shift to oppose the change

Question 5

A + B <> C + D
concentration of A is increased

Answer 5

1) equilibrium will shift to the right
2) oppose addition of A
3) so yield of C and D increases

Question 6

A + B <> C + D
concentration of A is decreased

Answer 6

1) equilibrium will shift to the left
2) oppose addition of A
3) so yield of A and B increases

Question 7

H2 + O2 <> H2O2

why would an industrial manufacturer of hydrogen peroxide increase the amount of hydrogen gas in the mixture ?

Answer 7

1) Equilibrium shifts right
2) To oppose addition of Hydrogen
3) Yield of Product increases

Question 8

3H2 + N2 <> 2NH3

pressure increased

Answer 8

1) fewer moles on the right
2) equilibrium shifts to the right to oppose the increase in pressure
3) so yield of NH3 increases

Question 9

3H2 + N2 <> 2NH3

pressure decreased

Answer 9

1) more moles on the left
2) equilibrium shifts to the left to oppose the decrease in pressure
3) so yield of H2 and N2 increases

Question 10

CH4 + H2O <> CO + 3H2

Use le Chateliers principle to explain why a low pressure should be used to obtain the highest equilibrium yield of H

Answer 10

1) More moles on the right
2) equilibrium shifts right to oppose decrease in pressure
3) yield of H increases

Question 11

When temp is decreased, equilibrium yield of product increases
3H2 + N2 <> 2NH3
is the forward reaction exo or endo ? explain

Answer 11

1) equilibrium shifts right to oppose decrease in temp
2) yield of NH3 increases
3) forward = exothermic

Question 12

Why does a catalyst not effect the position of equilibrium

Answer 12

Catalyst increase the rate of forward reaction and backward equally

Question 13

Why are catalysts added to the harbour process, which is a reversible reaction producing ammonia

Answer 13

to reduce the time taken to reach dynamic equilibrium

Question 14

Why are compromise conditions necessary ?

Answer 14

• Higher pressure would be too expensive
• 450’C gives a good yield in a fast time