3.4.2 Equilibrium - Aqa A2 Chemistry - Unit 4 - 3.4.2

Front 1

Dynamic Equilibrium:

1) Definition?

2) Conditions?

Back 1

1) The rates of the forwards and backwards reactions are exactly equal.

2) In a closed system at a constant temperature.

Front 2

Equilibrium can be one of three things:

– State them.

Back 2

– To the left.

– To the right.

– Dynamic.

Front 3

To calculate where the equilibrium lies:

1) We use?

2) Expression for this?

Back 3

1) Kc - this is known as the equilibrium constant and its value tells us the position of the equilibrium.

2) Kc = [Products]/[Reactants].

Front 4

Knowing the position of the equilibrium from Kc:

1) Dynamic equilibrium?

2) Favouring the forward reaction (to the right)?

3) Favouring the reverse reaction (to the left)?

Back 4

1) Kc = 0.

2) Kc > 1.

3) Kc < 1.

Front 5

To write a Kc expression:

Back 5

We do the concentrations of the reactants divided by the concentrations of the reactants, and the balancing numbers from the chemical equations are used as powers.

Front 6

Kc is affected by:

Back 6

Temperature ONLY.

Front 7

Impact on Kc when temperature is increased:

1) In exothermic reactions?

2) In endothermic reactions?

Back 7

1) Kc decreases as the equilibrium shifts to the endothermic side (reactants) and this is inversely proportional to Kc.

2) Kc increases as the equilibrium shifts to the endothermic side (products) and this is directly proportional to Kc.

Front 8

To calculate Kc:

Back 8

1) Write out the balanced chemical equation.

2) Write out the initial moles.

3) Add a used moles row.

4) Add a final moles row (we're usually given one of these).

5) Use our balancing numbers to then calculate how much of everything has been reacted.

6) Convert our final moles into concentration s and use the Kc equation.