Chemical equilibria

What is LE CHATELIERS PRINCIPLE [2]?

If the conditions of a system change, the position of the equilibrium shifts to counteract the change.

Catalysts have no effect on the equilibrium.

How does TEMPERATURE effect the position of the equilibrium?

→Increasing temperature:

Shifts to the endothermic side.

→Decreasing temperature:

Shifts to the exothermic side.

How does PRESSURE effect the position of the equilibrium?

→Increasing pressure:

Shifts to the side with fewer moles of gas.

→Decreasing pressure:

Shifts to the side with more moles of gas.

How does CONCENTRATION effect the position of the equilibrium?

→Increase in reactants // Decrease in reactants:

Shifts to the products. // Shifts to the reactants.

→Increase in products // Decrease in products:

Shifts to the reactants. // Shifts to the products.

Explain why reversible reactions used in industrial processes must use a compromised temperature & pressure? [4] (eg. Haber process)

• Industrial processes balance: rate, yield & cost. To maximise profit.

• Lower temp = favours exothermic side, BUT, slower rate of reaction. Higher temp = favours endothermic side.

• Lower pressure = favours side with more moles of gas. Higher pressure = favours side with fewer moles of gas, BUT, it is expensive & unsafe.

• Catalysts = faster rate, WITHOUT affecting equilibrium.

What is the Equilibrium constant? And how is it calculated?

The numerical value of the position of the equilibrium at a given temperature.

• Kc = ([C]^c [D]^d) divide ([A]^a [B]^b)

(Input: concentration OR the units of concentration)

What effect does the increase & decrease of temperature have on Kc (EXOTHERMIC EQUILIBRIUM) reaction?

• INCREASE in temp = shifts to the left = Kc DECREASES.

• DECREASE in temp = shifts to the right = Kc INCREASES.

What effect does the increase & decrease of temperature have on Kc (ENDOTHERMIC EQUILIBRIUM) reaction?

• INCREASE in temp = shifts to the right = Kc INCREASES.

• DECREASE in temp = shifts to the left = Kc DECREASES.

Define DYNAMIC EQUILIBRIUM [2]:

• When the concentrations of the products and reactants are the same.

• When the rate of the forward and backward reactions are the same.