CONTACT PROCESS

Question 1

What is the purpose of the contact process?

Answer 1

Sulphuric acid

Question 2

What do we use sulphuric acid for?

Answer 2

Cleaning agents
Fertilizers
Paint

Question 3

What are the raw materials used in the contact process?

Answer 3

Oxygen (in the air)
Sulphur
Water

Question 4

What is the chemical formula of sulphuric acid?

Answer 4

H2SO4

Question 5

What are the conditions needed for the contact process?

Answer 5

2 atmospheres

450˚

Question 6

What is the catalyst used in the contact process?

Answer 6

Vanadium (V) oxide

Question 7

What are the two ways you can introduce sulphur into the equation?

Answer 7

Pure sulphur
Sulphide ore (FeS2) also called pyrite

Question 8

What is the equation for the first stage of the contact process using pure sulphur?

Answer 8

S(s) + O2(g) –> SO2(g)

Question 9

What type of reaction is the first stage of the contact process (S(s) + O2(g) –> SO2(g))?

Answer 9

Oxidation reaction

Combustion reaction

Question 10

What is the equation for the alternative first stage of the contact process using pyrite (sulphide ore)?

Answer 10

4FeS2(s) + 11O2(g) –> 2Fe2O3(s) + 8SO2(g)

Question 11

What is the equation of the second stage of the contact process?

Answer 11

2SO2(g) + O2(g) 2SO3(g)

Question 12

Why must the second stage of the contact process be done in excess air?

Answer 12

To shift the reaction to the right and hence increase the amount of SO3 produced.

Question 13

Is the second stage of the contact process exothermic or endothermic?

Answer 13

Exothermic (∆H= -196 kJ/mol)

Question 14

As the second stage of the contact process is exothermic, theoretically would it be better to do this reaction at high or low temperatures?

Answer 14

Low temperature

Question 15

So if the second stage of the contact process would have a higher yield at a lower temperature, why do we do the reaction of 450˚?

Answer 15

Because the rate of the reaction would be too slow at a lower temperature. 450˚ is the compromise.

Question 16

Why do we do the reaction at 2 atmospheres?

Answer 16

Because there are 3 moles on the left side of the equation and there are 2 moles on the right. The right is therefore preferred at higher pressures. Therefore increasing the pressure will shift the reaction to the right.

Question 17

Does the catalyst increase the yield?

Answer 17

No. A catalyst never increases the yield. It only increases the rate.

Question 18

How does a catalyst work?

Answer 18

It provides an alternative pathway with a lower activation energy.

Question 19

What is activation energy?

Answer 19

The minimum amount of energy for the reaction to take place.

Question 20

What is the reaction in the third stage of the contact process?

Answer 20

SO3(g) + H2SO4(l) –> H2S2O7(l)

Question 21

What is another name for H2S2O7?

Answer 21

Oleum

Question 22

What is the equation for the fourth stage of the contact process?

Answer 22

H2S2O7(l) + H2O(l) –> 2H2SO4(aq)