3.2.3 Chemical Equilibrium

Question 1

Explain a dynamic equilibrium

Answer 1

A dynamic equilibrium exists in a closed system when the rate of the forward reaction is equal to the rate of the reverse reaction and the concentrations of reactants and products do not change

Question 2

what is le Chatelier’s principle?

Answer 2

If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change to re-establish the equilibrium

Question 3

How does an increase in temperature affect an equilibrium if the forward reaction is endothermic?

Answer 3

Endothermic reactions require heat to work, and so the forward reaction will be favoured, producing more products and so shifting the equilibrium to the right

Question 4

how does will decreasing the concentration of A in this equation effect the equilibrium?

A + B ⇌ C + D

Answer 4

it will favour the reverse (backwards) reaction because there will be less of A, and so the equilibrium will counteract this by using up C and D to make more A and so the equilibrium shifts to the left

Question 5

how does pressure effect the equilibrium in these 2 equations?

1) 2A (g) + B (g) ⇌ 3C (g) + D (s)
2) 2A (g) + B (g) ⇌ 3C (g) + D (g)

Answer 5

1) the equilibrium will not change, this is because D is a solid and will not be affected by pressure as it only applies to gasses, so there is no change
2) the equilibrium will shift to the reverse reaction, because there are more particles on the right side than the left, and so the equilibrium will shift to the left

Question 6

how will a catalyst effect an equilibrium?

Answer 6

It will not change the equilibrium only increase the rate of reaction for both sides

Question 7

What is the equilibrium constant? give the equation

Answer 7

Kc = [Products] / [Reactants]

make sure they are to the power of their ratio’s (the big number in front of the reactants/products

Question 8

What does the magnitude of Kc tell us?

Answer 8

Kc = 1: equilibrium lies halfway between the reactants and the products
Kc> (greater than)1: equilibrium lies further to the right and the products are favoured
Kc < (less than)1: equilibrium lies further to the left and the reactants are favoured