FC25: Equilibria

Question 1

give the definition of chemical equilibria

Answer 1

in a reversible reaction, equilibrium is reached when the rate of the forward and reverse reactions are equal

Question 2

What are 3 conditions for a dynamic equilibrium

Answer 2

1- the rates of the forward and reverse reactions are equal
2 - it is a closed system
3 - physical properties are kept constant (temp, pressure for gases etc)

Question 3

State Le Châtelier’s principle

Answer 3

If a condition that can affect the position of equilibrium is changed, the equilibrium will shift to oppose the change made

Question 4

What happens to the concentration of a product if the temperature is increased for an exothermic reaction

Answer 4

If temperature is increased, the reverse endothermic reaction is favoured, the equilibrium shifts to the left hand side to oppose the increase in temperature, this decreases the concentration of the product

Question 5

What happens to the yield of a product when the pressure of a gaseous mixture is increased, where the number of moles of gas are higher for the RHS than LHS

Answer 5

increasing the pressure, favours the reverse reaction to produce fewer moles of gas, so the equilibrium shifts to the left hand side, and the yield of the product decreases

Question 6

What is the effect of a catalyst on an equilibrium

Answer 6

Adding a catalyst lowers the activation energy of both the forward and reverse reactions equally, therefore neither reaction is favoured over the other and the position of the equilibrium is unchanged. However, equilibrium is reached faster

Question 7

If a high pressure is favourable, what is the risk of using high pressures in chemical industry

Answer 7

expensive to generate and require more expensive reaction vessels that can withstand these high pressures

Question 8

If a low temperature is favourable, what is the issue of using low temperatures in chemical industry

Answer 8

too low of a temperature will reduce the rate of reaction