Contact process

Question 1

The Contact process involves the

Answer 1

synthesis of sulfuric acid according to:
2SO­2(g) + O2(g) ⇌ 2SO3(g) ΔHr = -197 kJ mol-1

SO3 + H2SO4 → H2S2O7

H2S2O7 + H2O → 2H2SO4

Le Chatelier’s principle is used to get the best yield of sulfuric acid

Question 2

Maximising the sulfuric acid yield
Pressure

An increase in pressure will result in the equilibrium shifting in the direction of the fewest molecules of gas formed to reduce the pressure
In this case, the equilibrium shifts towards the

Answer 2

right so the yield of sulfur trioxide increases

Question 3

In practice, the reaction is carried out at only 1 atm
This is because Kc for this reaction

Answer 3

is already very high meaning that the position of the equilibrium is already far over to the right

Question 4

Higher pressures than 1 atm will be

Answer 4

unnecessary and expensive

Question 5

Temperature

The same principle applies to increasing the temperature in the Contact process as in the

a compromise temp of,……… is used

Answer 5

Haber process

450 degrees

Question 6

Removing sulfuric acid

In practice, SO3 is removed by absorbing it in……

why do this

Answer 6

98% sulfuric acid

This is because adding SO3 directly to water produces an uncontrollable and hazardous exothermic reaction

Question 7

The SO3 reacts with the sulfuric acid to make

Answer 7

oleum, H2S2O7, which is then carefully diluted to make more H2SO4

Question 8

Catalysts

The Contact process uses ………… as a catalyst to increase the rate of reaction

Answer 8

vanadium(V) oxide