Reversible Reactions

Question 1

What is the effect of heat on ammonium chloride?

Answer 1

• the thermal decomposition of ammonium chloride is a reversible reaction
• ammonium chloride is a white solid - when it’s heated it breaks down into the gases ammonia and hydrogen chloride (forward reaction)
• when cooled, the ammonia and hydrogen chloride react to reform a solid (backward reaction)

Question 2

How does a reversible reaction reach a dynamic equilibrium?

Answer 2

• when a reversible reaction takes place in a closed system (sealed container) then a state of equilibrium will be reached

Question 3

What is an equilibrium?

Answer 3

• equilibrium means that the concentration of reactants and products will reach a certain balance and stay there

Question 4

What are the characteristics of a reaction at dynamic equilibrium?

Answer 4

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

Question 5

What effect does a catalyst have on the position of equilibrium?

Answer 5

• adding a catalyst has no effect because it speeds up the forward reaction and the backward reaction by the same amount

Question 6

What can effect the position of equilibrium

Answer 6

• temperature
• pressure

Question 7

What effect does temperature have on the position of equilibrium

Answer 7

• if you raise the temperature, the endothermic reaction will increase to use up the extra heat
• if you reduce the temperature, the exothermic reaction will increase to give out more heat

Question 8

What effect does pressure have on the position of equilibrium?

Answer 8

• if you raise the pressure it will encourage the reaction which produces fewer moles of gas
• if you lower the pressure it will encourage the reaction which produces more moles of gas