Physical Chemistry - Reversible Reactions and Equilibria (Paper 2)

Question 1

when is dynamic equilibrium reached?

Answer 1

dynamic equilibrium can only be achieved in a sealed container so substances cannot escape

Question 2

what are the characteristics of a reaction at dynamic equilibrium?

Answer 2

• the forward and reverse reactions occur at the same rate
• the concentrations of reactants and products remain constant

Question 3

why doesn’t a catalyst affect the position of equilibrium?

Answer 3

• in a reversible reaction a catalyst speeds up both the forward and backward reactions
• so the position of equilibrium is not changed

Question 4

what does changing the temperature do to the position of equilibrium?

Answer 4

• all reactions are exothermic in one direction and endothermic in the other way
• if temperature is decreased the position of the equilibrium will shift to the exothermic direction
• if temperature is increased the position of the equilibrium will shift to the endothermic direction

Question 5

what does changing the pressure do to the position of equilibrium?

Answer 5

• reactions may have more molecules of gas on one side than on the other
• if the pressure is increased the position of the equilibrium will shift to the side with fewer molecules
• if the pressure is decreased the position of the equilibrium will shift to the side with more molecules