Equilibria

Question 1

When is a reaction at equilibrium?

Answer 1

• When a balance of reactants and products is reached
• Rate of forward reaction = rate of backward reaction
• Concentration of reactions and products don’t change

Question 2

What happens during an equilibrium reaction?

Answer 2

• Initially the rate of the forward reaction is faster but it slows down as the reactants are used up
• The backward reaction rate increases as more product is available to react
• Eventually the forward and backward reaction reach the same rate

Question 3

When is the only time an equilibrium is possible?

Answer 3

In a closed system.

Question 4

How does temperature affect the equilibria?

Answer 4

If temperature is increased the equilibria will shift in the direction of the endothermic reaction to balance out the heat.

Question 5

How does pressure affect the equilibria?

Answer 5

If pressure is increased the equilibria will shift to the side with the least number of moles.

Question 6

How does concentration affect the equilibria?

Answer 6

The concentration of reactants and products don’t change but there are not equal. If the concentration is higher on the reactants side, the equilibria lies on the left and vice versa.

Question 7

What is the equation for the contact process?

Answer 7

Sulphur dioxide + oxygen —> sulphur trioxide

2SO2 + O2 —> 2SO3

Question 8

What conditions does the contact process use and why?

Answer 8

• 450*C because the forward reaction is exothermic so a high temperature would shift the equilibria to the left but a temperature too low would decrease the rate of reaction so it is a compromise
• High pressure increases the yield because there are more gas molecules on the left of the equation so the equilibria shifts to the right
• Catalysts don’t affect the position of the equilibria but they increase the rate of reaction