Equilibrium

Question 1

What does reversible mean?

Answer 1

Reaction which goes in both forward and backward directions.

Question 2

What does dynamic equilibrium mean?

Answer 2

Rate of forward reaction equal to rate of backward reaction and amounts of reactant and product remains constant.

Question 3

What does homogeneous mean?

Answer 3

Reaction in which all reactants and products are in same physical state.

Question 4

What does Le Chatelier’s Principle state?

Answer 4

If dynamic equilibrium is disturbed by changing the conditions, position of the equilibrium will move to counteract the change.

Question 5

What conditions can be changed in a closed homogeneous system?

Answer 5

Concentration
Pressure
Temperature

Question 6

What are the effects of changing concentration in a closed homogeneous system?

Answer 6

If more of a chemical is added equilibrium position moves to remove it.

If some of a chemical is removed equilibrium position moves to make more of it.

Question 7

What are the effects of changing pressure in a closed homogeneous system?

Answer 7

To increases pressure, position of equilibrium moves to side with most gas molecules.

To decrease pressure, position of equilibrium moves to side with least gas molecules.

Question 8

What are the effects of changing temperature in a closed homogeneous system?

Answer 8

Increasing temperature of system in dynamic equilibrium favours endothermic reaction.
System counteracts change made by absorbing the extra heat.

Decreasing temperature of system in dynamic equilibrium favours exothermic reaction.
System counteracts change made by producing more heat.

Question 9

What is the composition of air?

Answer 9

78% nitrogen
21% oxygen
1% argon
0.03%-0.04% carbon dioxide
Small proportions of noble gases (except argon)
Varying proportions of water vapour

Question 10

What are the physical properties of nitrogen?

Answer 10

Colourless gas
Odourless gas
Diatomic
Insoluble in water

Question 11

What are the uses of nitrogen?

Answer 11

As a coolant
In food packaging
In manufacture of ammonia

Question 12

What are the uses of ammonia?

Answer 12

Manufacture of fertilisers - ammonia is reacted with acids to from ammonium salts; salts used in fertilisers and provide plants with nitrogen which is good for their growth.

Production of nitric acid

Manufacture of nylon

Question 13

What is the test for ammonia?

Answer 13

Hold glass rod dipped in concentrated hydrochloric acid near the gas.
If ammonia is present white smoke is formed.

Ammonia + hydrogen > ammonium chloride

Question 14

What is the symbol equation for the Haber process?

Answer 14

N2(g) + 3H2(g) <> 2NH3(g)

^H = -92KJ-1

Question 15

What are the conditions used in the Haber process?

Answer 15

Pressure is 200 atmospheres
Temperature is 450oC
Iron catalyst

Question 16

What is the effect of pressure in the Haber process?

Answer 16

High pressure would move position of equilibrium to right-hand side where there are fewer molecules.

Very high pressures are very expensive to produce as need to build extremely strong pipes and containment vessels to withstand very high pressure and it costs a lot to produce and maintain.

Question 17

What is the effect of a catalyst in the Haber process?

Answer 17

Iron catalyst has no effect on position of equilibrium.

Question 18

What is the effect of temperature in the Haber process?

Answer 18

Forward reaction is exothermic and according to Le Chatelier’s principle this will be favoured by decreasing temperature.

Lower the temperature used, slower the rate of reaction.