Topic 5.19-5.24 - Dynamic equilibria

Question 1

Describe the Haber process

Answer 1

A reversible reaction between nitrogen and hydrogen to form ammonia

Question 2

Predict how the rate of attainment of equilibrium is affected by changes in temperature

Answer 2

Equilibrium​ ​is​ ​reached​ ​at​ ​a​ ​faster​ ​rate​ ​when a​ ​higher​ ​temperature​ ​is​ ​used​ ​(particles​ ​have​ ​more​ ​kinetic​ ​energy​ ​so​ ​collide​ ​more frequently​ ​so​ ​have​ ​more​ ​successful​ ​collisions)

Question 3

Predict how the rate of attainment of equilibrium is affected by changes in pressure and/or concentration

Answer 3

Equilibrium​ ​is​ ​reached​ ​at​ ​a​ ​faster​ ​rate​ ​when a​​ ​higher​ ​pressure/concentration​ ​is​ ​used​ ​(more​ ​particles​ ​in​ ​a​ ​given​ ​volume,​ ​so more​ ​frequent​ ​successful​ ​collisions)

Question 4

Predict how the rate of attainment of equilibrium is affected by the use of a catalyst

Answer 4

Equilibrium​ ​is​ ​reached​ ​at​ ​a​ ​faster​ ​rate​ ​

Question 5

Explain the conditions, in industrial reactions, used for the Haber process

Answer 5

For the Haber process - ​the purified gases are passed over a catalyst of iron at a high​temperature​ ​(about​ ​450​ ​°C)​ ​and​ ​a​ ​high​ ​pressure​ ​(about​ ​200​ ​atmospheres).

Question 6

Explain what the conditions in industry reactions are related to and why

Answer 6

-High​ ​temperatures​ ​and​ ​pressures​ ​are​ ​desired​ ​for​ ​industrial​ ​reactions​ ​to increase​ ​the​ ​rate​ ​of​ ​reaction
-But,​ ​a​ ​higher​ ​temperature​ ​shifts​ ​equilibrium​ ​towards​ ​the​ ​reactants​ ​(as the​ ​forwards​ ​reaction​ ​is​ ​exothermic),​ ​therefore​ ​a​ ​compromise​ ​is​ ​required to​ ​ensure​ ​a​ ​fast​ ​rate​ ​of​ ​reaction​ ​and​ ​a​ ​high​ ​yield​ ​of​ ​products
-Catalyst​ ​is​ ​used​ ​because​ ​of​ ​the​ ​effect​ ​of​ ​having​ ​an​ ​increased​ ​rate​ ​of reaction,​ ​however​ ​they​ ​are​ ​also​ ​expensive
-High​ ​temperatures​ ​and​ ​pressures​ ​can​ ​be​ ​expensive​ ​and​ ​dangerous​ ​as​ ​well (particularly​ ​pressures)​ ​and​ ​the​ ​equipment​ ​required​ ​for​ ​them​ ​can​ ​be​ ​very expensive

Question 7

What may fertilisers contain and why?

Answer 7

Fertilisers may contain nitrogen, phosphorus and potassium compounds to promote plant growth.

NPK fertilisers contain compounds of all 3.

Question 8

Describe how ammonia reacts with nitric acid

Answer 8

Ammonia acts as a base. They react to produce a salt, ammonium nitrate, which can be used as a fertiliser

Question 9

Describe the laboratory preparation of ammonium sulfate

Answer 9

The reactants are ammonia solution and dilute sulphuric acid (bought from chemical manufacturers). This is done on a small scale and only includes a few stages (titration, then crystallisation)

Question 10

Describe the industrial production of ammonium sulfate

Answer 10

The reactants are natural gas, air and water to make ammonia and sulphur, air and water to make sulphuric acid. This is done on a large scale and requires many stages, including making the ammonia and sulphuric acid, reacting accurate volumes and then evaporating it.