6.2 Reversible reactions and dynamic equilibrium (Triple)

Question 1

What is a reversible reaction?

Answer 1

A reversible reaction occurs when the products of a reaction can react backwards
to produce the original reactants

Question 2

When is dynamic
equilibrium reached?

Answer 2

In a closed system, when the forward and reverse reactions occur at the same rate
and the concentrations of reactants and products remain constant.

Question 3

Describe Le Chatelier’s
Principle

Answer 3

If a system is at equilibrium and a change is made to any of the conditions, then
the system responds to counteract change and restore the equilibrium.

Question 4

Describe the effect of changing the concentration of
reactant and product on the
position of the equilibrium. (Triple)

Answer 4

If the concentration of one of the reactants or products is changed, the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again.

If the concentration of a reactant is increased, more products will be formed until equilibrium is reached again.

If the concentration of a product is decreased, more reactants will react until equilibrium
is reached again.

Question 5

Describe the effect of changing temperature on the position of the equilibrium. (Triple)

Answer 5

If the temperature of a system at equilibrium is
increased:

● The relative amount of products at equilibrium increases for an endothermic
reaction

● The relative amount of products at equilibrium decreases for an exothermic
reaction.

Question 6

Describe the effect of changing pressure on the
position of the equilibrium. (Triple)

Answer 6

This applies to equilibria that involve gases.

An increase in pressure causes the equilibrium position to shift towards the side
with the smaller number of molecules as shown by the symbol equation for that
reaction.

A decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction.

Pressure has no effect on the reactions where the numbers of gas molecules are equal on both sides of the equation.

Question 7

Describe the effect of a catalyst on the position of the
equilibrium. (Triple)

Answer 7

No effect.

It just speeds up both forward and backward reactions equally. i.e. equilibrium is achieved faster.