Industrial Processes

Question 1

What is the Haber Process?

Answer 1

A way of manufacturing ammonia.

Question 2

What is the chemical equation for the Haber process?

Answer 2

N_2(g) + 3H_2(g) → 2NH_3(g) + heat

Question 3

How are the reactants in the Haber processs obtained?

Answer 3

• Nitrogen is easily obtained from the air (air is 78% N₂).
• Hydrogen is obtained from methane (natural gas) or naptha.
  
  • it is reacted with steam to form carbon dioxide and hydrogen
  • CH_4(g) + 2H₂O_(g) → CO_2(g) + 4H_2(g)

Question 4

What are the industrial conditions in the Haber process?

Answer 4

• A temperature at about 450ºC.
• A pressure of about 200 atmospheres.
• A catalyst of iron.

Question 5

During the Haber process, how does cooling the gases allow ammonia to be separated from the unused reactants, and what happens to the unused reactants?

Answer 5

• Ammonia condenses at a higher temperature than hydrogen and nitrogen, so when the gases cool it is the first to condense and can be separated.
• The unused hydrogen and nitrogen are recycled and used again.

Question 6

What are three uses of ammonia?

Answer 6

1. Nylon.
2. Fertiliser.
3. Nitric acid.

Question 7

Why is the temperature in the Haber process a compromising factor?

Answer 7

• A higher temperature would decrease the yield of ammonia, because the forward reaction is exothermic so increasing the heat shifts equilibrium in the direction of the backwards reaction.
• Having a temperature any lower than 450ºC would mean that the reaction would be too slow, as there would be less kinetic energy.
• The temperature is a compromise between maximum yield and speed of reaction.

Question 8

Why is the pressure in the Haber process a compromising factor?

Answer 8

• Increasing the pressure would increase the yield of ammonia, because increasing the pressure shifts equilibrium in the direction of the forwards reaction (because there are more moles of reactants).
• A pressure higher than 200 atmospheres would make the too expensive.

Question 9

What is the contact process?

Answer 9

A method of making sulphuric acid.

Question 10

What raw materials are used in the manufacture of sulphuric acid (contact process)?

Answer 10

• Sulphur, which is found from sulphur deposits and rocks.
• Oxygen (found in the air and water).

Question 11

What happens during the contact process to make the sulphuric acid (without chemical reactions)?

Answer 11

1. Sulphur is burned in an excess of air to make sulphur dioxide gas.
2. Sulphur dioxide is oxidised (with a catalyst) to form sulphur trioxide gas.
3. Sulphur trioxide is dissolved in sulphuric acid to produce oleum.
4. The oleum is dissolved in water to form concentrated sulphuric acid.

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Question 12

What are the chemical reactions for each stage of the contact process?

Answer 12

1. S_(s) + O_2(g) → SO_2(g)
2. 2SO_2(g) + O_2(g) ⇌ 2SO_3(g)
3. SO_3(g) + H₂SO_4(l) → H₂S₂O_7(l)
4. H₂S₂O_7(l) + H₂O_(l) → 2H₂SO_4(l)

Question 13

What are the essential conditions for the contact process?

Answer 13

• A temperature of about 450ºC.
• A pressure of about 2 atmospheres.
• A catalyst of vanadium oxide.

Question 14

What are some of the uses of sulphuric acid?

Answer 14

Manufacture of many products such as:

• detergents
• paints
• fertilisers

Question 15

How are sodium hydroxide and chlorine manufactured?

Answer 15

The electrolysis of aqueous sodium chloride solution (brine).

Question 16

What happens during the electrolysis of brine?

Answer 16

• Hydrogen gas is formed at the cathode from positive hydrogen ions and electrons.
• Chlorine gas is formed at the anode from negative chloride ions losing electrons.
• Sodium hydroxide (NaOH) is left in the solution from sodium ions and hydroxide ions being left.

Question 17

What is the half-equation for the reaction at the cathode during the electrolysis of brine?

Answer 17

2H⁺_(aq) + 2e^- → H_2(g)

Question 18

What is the half-equation for the reaction at the anode during the electrolysis of brine?

Answer 18

2Cl^-_(aq) → Cl₂ + 2e^-

Question 19

What are the uses of chlorine?

Answer 19

• _Sterilising wate_r (killing bacteria) in pools and drinking water.
• Manufacture of bleach, and hydrochloric acid.

Question 20

What are the uses of sodium hydroxide?

Answer 20

• Manufacture of bleach, paper and soap.

Question 21

What are the uses of hydrogen?

Answer 21

• Converting oils into fats for margarine.
• Taking part in the Haber process.