Section 4 - Pg 64

Question 1

What is a reversible reaction?

Answer 1

Where the products can react with each other and convert back to the original reactants.

Question 2

How is a reversible reaction symbolised?

Answer 2

In the equation, the arrow points both ways.

Question 3

What is the word equation for the thermal decomposition of ammonium chloride?

Answer 3

Ammonium chloride (s) Ammonia (g) + Hydrogen chloride (g)

The reaction is reversible.

Question 4

What is the symbol equation for the thermal decomposition of ammonium chloride?

Answer 4

NH4Cl (s) NH3 (g) + HCl (g)

The reaction is reversible.

Question 5

Describe the thermal decomposition of ammonium chloride.

Answer 5

1) Ammonium chloride is a white solid.
2) When heated, it breaks down into the gases ammonia and hydrogen chloride.
3) When it cools, the two gases react to re-form the solid ammonium chloride.

Question 6

What colour is ammonium chloride?

Answer 6

White

Question 7

Give 2 examples of reversible reactions.

Answer 7

1) Thermal decomposition of ammonium chloride.

2) Dehydration of copper(II) sulphate (the test for water).

Question 8

What is equilibrium?

Answer 8

The state at which the relative (%) quantities of reactants and products reach a certain balance and stay there.

Question 9

Where can an equilibrium be reached?

Answer 9

In a closed system.

Question 10

What is a dynamic equilibrium?

Answer 10

An equilibrium where the backwards and forwards reactions take place at the same rate but the overall effect is nil because they cancel each other out.

Question 11

What two factors can change the position of an equilibrium?

Answer 11

1) Temperature

2) Pressure

Question 12

What effect does increasing the temperature have on the position of the equilibrium?

Answer 12

• If you raise the temperature, the endothermic reaction will increase to use up the extra heat (to try and revert to the previous temperature).

Question 13

What effect does decreasing the temperature have on the position of the equilibrium?

Answer 13

• If you reduce the temperature, the exothermic reaction will increase to give out more heat (to try and revert to the previous temperature).

Question 14

What effect does increasing the pressure have on the position of the equilibrium?

Answer 14

• If you raise the pressure, it will encourage the reaction which produces fewer molecules of GAS (to try and revert to the previous lower pressure).

Question 15

What effect does decreasing the pressure have on the position of the equilibrium?

Answer 15

• If you lower the pressure, it will encourage the reaction which produces more molecules of GAS (to try and revert to the previous higher pressure).