Reversible Reactions & Equilibrium (Cambridge (CIE) IGCSE Chemistry)

Increasing the pressure would favour the forward reaction.

This is because there are 4 molecules on the left and side and 2 molecules on the right hand side.

An increase in pressure will favour the side with the fewest number of molecules.

If the forward reaction is endothermic, a high temperature would increase the yield of products.

This is because the forward reaction is endothermic. A high temperature would favour the endothermic pathway to oppose the increase.

False.

An endothermic reaction is represented by a positive enthalpy change.

False.

Increasing pressure shifts the equilibrium to favour the side with fewer gas molecules.

Decreasing the concentration of a product shifts the equilibrium to the left, favouring the reactants.

Equilibrium shifts to the left to reduce the effect of a decrease in reactant (or an increase in the concentration of product).

Equilibrium shifts in the direction that produces the larger number of molecules of gas to increase the pressure again.

In a reversible reaction, the concentration of the reactants is highest at the start of the reaction.

Dynamic equilibrium is where the rate of the forward reaction equals the rate of the reverse reaction, and the concentrations of reactants and products remain constant.

A closed system is a system where none of the reactants or products can enter or leave the reaction vessel.

An open system is a system where the reactants or products can both enter or leave the reaction vessel.

True.

Dynamic equilibrium can only occur in a closed system as none of the reactants or products are able to leave the reaction vessel.

The Haber Process is the industrial process for manufacturing ammonia from nitrogen and hydrogen gases.

The equation for the Haber Process is:

N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)

The catalyst used in the Haber Process is iron.

False.

Decreasing the temperature of the Haber Process will produce a high yield of ammonia. This is because the forward reaction is exothermic (ΔH=−92.4 kJ/mol)

Compromise conditions are the conditions chosen to give a good balance between product yield, reaction rate and production cost, rather than ideal conditions for any one factor.

True.

Increasing the pressure of the Haber Process will produce a high yield of ammonia. This is because there are more gaseous molecules on the left hand side.

N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)

The compromise temperature used is 450 °C.

The compromise pressure used is 200 atm.

A compromise temperature is used to balance having a lower yield of products but being made more quickly.

A compromise pressure is used to balance a lower yield of products being made safely and economically.

Ammonia is removed from the reaction vessel by being cooled and liquified.

The unreacted hydrogen and nitrogen gases are recycled back into the system and start over again

Hydrogen is obtained from natural gas and nitrogen is obtained from the air.

The main product of the Contact process is sulfuric acid.

False.

The oxygen used in the Contact process is obtained from air.

The catalyst used in the main stage of the Contact process is vanadium(V) oxide, V₂O₅.

A compromise temperature of 450°C is used in the Contact process because it balances the need for a higher yield of products with the need for a faster reaction rate.

True.

The Contact process is an example of a reversible reaction.

Three major applications of concentrated sulfuric acid produced by the Contact process are use in car batteries, making fertilisers, and making soaps and detergents.

The balanced equation is:

2SO₂ + O₂    2SO₃

A high pressure will favour the production of SO₃.

2SO₂ + O₂    2SO₃

A low temperature favours the production of SO₃.

A high pressure is not used in the Contact process because:

• High pressures can be dangerous and very expensive equipment is needed 

• A higher pressure causes the sulfur dioxide to liquify