In a reaction that goes to completion in an open system, the amount of reactant falls from its original value to zero. At the same time, the amount of product increases from zero to a maximum amount.

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What do the slopes of the red and blue graphs tell us?

The slopes tell us about the rate of reaction.

Why are the slopes of the graphs steep in the initial stages of the reaction?

In the initial stages of the reaction the rate of reaction is fast.

Why do the slopes of the graphs become less steep?

The rate of reaction decreases as the reactant is used up and its concentration falls.

In a reaction in which an equilibrium is established in a closed system, the amount of reactant falls from its original value to a lower value at which it remains constant. At the same time the amount of product increases from zero to reach a value at which it remains constant.

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What happens to the rate of the reaction in which the product is formed from the start of the reaction to when an equilibrium is established?

The rate of reaction decreases until it reaches a constant value.

What happens to the rate of the reaction in which the reactant is formed from the start of the reaction to when the equilibrium is established?

The rate of reaction increases until it reaches a constant value.

What can you say about the rate of the forward and the rate of the reverse reaction when equilibrium has been established?

At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction.

How can you tell from the graph that equilibrium has been established?

The slopes of both graphs become horizontal.

What can you say about the amounts of reactant and product when equilibrium is established?

The amounts of reactant and product in the equilibrium mixture are constant. They don't change – but that doesn't mean that they are the same.