Topic 4.13-4.17 - Reversible reactions and equilibria

Question 1

Explain reversible reactions

Answer 1

In reversible reactions, both the forwards and backwards reactions can occur under the right conditions. the​ ​⇌​ ​symbol​ ​is​ ​used​ ​to​ ​show​ ​that​ ​a​ ​reaction​ ​is​ ​reversible

Question 2

Explain what is meant by dynamic equilibrium

Answer 2

Once the forward and backward reaction has reached a dynamic equilibrium the concentrations of reactants and products remain constant. If this is disturbed by changing conditions the equilibrium position changes to counteract the change

Question 3

Describe the formation of ammonia

Answer 3

It is a reversible reaction between Nitrogen (extracted from the air) and hydrogen (obtained from natural gas) and it can reach a dynamic equilibrium.

Question 4

What is the equation for The Haber Process?

Answer 4

N₂+3H₂ ⇌ 2NH₃

Question 5

Recall the conditions for The Haber Process

Answer 5

-A temperature of 450℃
-Pressure 200 atmospheres
-An iron catalyst

The purified gases are passed over a catalyst of iron at this temperature and pressure.

Question 6

How is the position of a dynamic equilibrium affected by a change in temperature?

Answer 6

If temperature is increased, the equilibrium moves in the direction of the endothermic reaction. It absorbs heat from the surroundings and the temperature of the surroundings will decrease.

If temperature is decreased the equilibrium moves in the direction of the exothermic reaction

Question 7

How is the position of a dynamic equilibrium affected by a change in pressure?

Answer 7

In gaseous reactions, an increase in pressure will favour the reaction that produces the least number of molecules.

A decrease in pressure will increase the yield of the reaction that produces the large volume of gas/number of moles/number of molecules.

Question 8

How is the position of a dynamic equilibrium affected by a change in concentration?

Answer 8

If the concentration of reactants is increased the position of equilibrium shifts towards the product (right) so more product is produced until equilibrium is reached again.

If the concentration of products is increased the position of the equilibrium shifts towards the reactants (left) so more reactant is produced until equilibrium is reached again.