IGCSE CHEMISTRY SECTION 5 LESSON 4

Content The iGCSE Chemistry course Section 1 Principles of Chemistry Section 2 Chemistry of the Elements Section 3 Organic Chemistry Section 4 Physical Chemistry Section 5 Chemistry in Society

Content Section 5 Chemistry in industry a)Extraction and uses of metals b)Crude oil c)Synthetic polymers d)The industrial manufacture of chemicals

Lesson 4 d) The industrial manufacture of chemicals 5.22 understand that nitrogen from air, and hydrogen from natural gas or the cracking of hydrocarbons, are used in the manufacture of ammonia 5.23 describe the manufacture of ammonia by the Haber process, including the essential conditions: i a temperature of about 450°C ii a pressure of about 200 atmospheres iii an iron catalyst 5.24 understand how the cooling of the reaction mixture liquefies the ammonia produced and allows the unused hydrogen and nitrogen to be recirculated 5.25 describe the use of ammonia in the manufacture of nitric acid and fertilisers 5.26 recall the raw materials used in the manufacture of sulphuric acid 5.27 describe the manufacture of sulphuric acid by the contact process, including the essential conditions: i a temperature of about 450°C ii a pressure of about 2 atmospheres iii a vanadium(V) oxide catalyst 5.28 describe the use of sulphuric acid in the manufacture of detergents, fertilisers and paints 5.29 describe the manufacture of sodium hydroxide and chlorine by the electrolysis of concentrated sodium chloride solution (brine) in a diaphragm cell 5.30 write ionic half-equations for the reactions at the electrodes in the diaphragm cell 5.31 describe important uses of sodium hydroxide, including the manufacture of bleach, paper and soap; and of chlorine, including sterilising water supplies and in the manufacture of bleach and hydrochloric acid.

The Industrial Manufacture of Chemicals 1. The Haber Process - Ammonia, NH 3 2. The Contact Process – Sulphuric acid 3. Sodium hydroxide and Chlorine

#1 The Haber Process

What’s this all about?

#1 The Haber Process Plants need nutrients in order to survive. To improve crop yields, farmers spread fertilisers on their fields. These fertilisers contain minerals essential for healthy plant growth.

#1 The Haber Process During World War I, blockades of Germany by the Allies meant that the German farmers could not get any access to natural fertilisers from South America. In order to prevent mass starvation, German chemists developed a process for making ammonia from atmospheric nitrogen.

#1 The Haber Process Fritz Haber developed the first practical process to convert atmospheric nitrogen into ammonia. From ammonia fertilisers could be made. Fertiliser generated from ammonia produced by the Haber process is estimated to be responsible for sustaining one- third of the Earth’s population.

#1 The Haber Process The nitrogen-rich fertiliser ammonium nitrate is used regularly by farmers, and spread in huge quantities on crops around the world.

#1 The Haber Process The Basics!

#1 The Haber Process The Basics! The Haber Process produces ammonia which is needed for making fertilisers.

#1 The Haber Process The Basics! The Haber Process produces ammonia which is needed for making fertilisers. Nitrogen is obtained easily from the air which is 78% nitrogen.

#1 The Haber Process The Basics! The Haber Process produces ammonia which is needed for making fertilisers. Nitrogen is obtained easily from the air which is 78% nitrogen. Hydrogen is obtained from water (steam) and natural gas (methane, CH 4 )

#1 The Haber Process The Basics! The Haber Process produces ammonia which is needed for making fertilisers. Nitrogen is obtained easily from the air which is 78% nitrogen. Hydrogen is obtained from water (steam) and natural gas (methane, CH 4 ) The Haber Process is a reversible reaction.

#1 The Haber Process The Basics! N 2(g) + 3H 2(g) 2NH 3(g) nitrogen hydrogen ammonia Reversible reaction

#1 The Haber Process The Basics! Industrial Conditions: PRESSURE: 200 atmospheres TEMPERATURE: 450 o C CARALYST: Iron

#1 The Haber Process Reaction vessel Trays of iron catalyst Condenser 450 o C and 200 atm

#1 The Haber Process Reaction vessel Trays of iron catalyst Condenser H 2 and N 2 mixed in 3:1 ratio 450 o C and 200 atm 1. The hydrogen and nitrogen are mixed together in a 3:1 ratio

#1 The Haber Process Reaction vessel Trays of iron catalyst Condenser H 2 and N 2 mixed in 3:1 ratio 450 o C and 200 atm 1. The hydrogen and nitrogen are mixed together in a 3:1 ratio

#1 The Haber Process Reaction vessel Trays of iron catalyst Condenser H 2 and N 2 mixed in 3:1 ratio 450 o C and 200 atm 1. The hydrogen and nitrogen are mixed together in a 3:1 ratio 2. Because the reaction is reversible, not all of the N 2 and H 2 will convert to ammonia. 3. The NH 3 is formed as a gas but as it cools in the condenser it liquefies and is removed. Liquid ammonia

#1 The Haber Process Reaction vessel Trays of iron catalyst Condenser H 2 and N 2 mixed in 3:1 ratio 450 o C and 200 atm 1. The hydrogen and nitrogen are mixed together in a 3:1 ratio 2. Because the reaction is reversible, not all of the N 2 and H 2 will convert to ammonia. 3. The NH 3 is formed as a gas but as it cools in the condenser it liquefies and is removed. Liquid ammonia 4. The N 2 and H 2 which didn’t react are recycled in the system Unused N 2 and H 2 are recycled

Two important reactions involving ammonia

#1 Making Nitric Acid

Two important reactions involving ammonia A two stage reaction: a)Ammonia gas reacts with oxygen over a hot platinum catalyst 4NH 3(g) + 5O 2(g)  4NO (g) + 6H 2 O (g)

Two important reactions involving ammonia A two stage reaction: a)Ammonia gas reacts with oxygen over a hot platinum catalyst 4NH 3(g) + 5O 2(g)  4NO (g) + 6H 2 O (g) A very exothermic reaction, the nitrogen monoxide must be cooled before the next stage.

Two important reactions involving ammonia A two stage reaction: a)Ammonia gas reacts with oxygen over a hot platinum catalyst 4NH 3(g) + 5O 2(g)  4NO (g) + 6H 2 O (g) b)The nitrogen monoxide reacts with water and oxygen: 6NO (g) + 3O 2(g) + 2H 2 O (g)  4HNO 3(g) + 2NO (g)

Two important reactions involving ammonia A two stage reaction: a)Ammonia gas reacts with oxygen over a hot platinum catalyst 4NH 3(g) + 5O 2(g)  4NO (g) + 6H 2 O (g) b)The nitrogen monoxide reacts with water and oxygen: 6NO (g) + 3O 2(g) + 2H 2 O (g)  4HNO 3(g) + 2NO (g) The nitric acid produced can then be used to make ammonium nitrate fertiliser

Two important reactions involving ammonia #2 Making Ammonium Nitrate fertiliser

Two important reactions involving ammonia This is a simple neutralisation reaction between and acid and an alkali to produce a neutral salt. NH 3(aq) + HNO 3(aq)  NH 4 NO 3(aq) Ammonium nitrate is a particularly good fertiliser because it has nitrogen from two sources – ammonia and nitric acid.

The Industrial Manufacture of Chemicals 1. The Haber Process - Ammonia, NH 3 2. The Contact Process – Sulphuric acid 3. Sodium hydroxide and Chlorine

“describe the manufacture of sulphuric acid by the contact process, including the essential conditions”

The Contact Process Sulphuric Acid H 2 SO 4

The Contact Process Sulphuric Acid H 2 SO 4 Raw materials: sulphur, oxygen, water

The Contact Process Sulphuric Acid H 2 SO 4 Raw materials: sulphur, oxygen, water Conditions: Catalyst (vanadium oxide) Pressure of 2 atmospheres Temperature of about 450 o C

The Contact Process Three stage process.

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g)

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g) Sulphur is burnt in air (or sulphur ore may be used)

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g) 2. Preparation of sulphur oxide 2SO (s) + O 2(g) 2SO 3(g)

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g) 2. Preparation of sulphur oxide 2SO (s) + O 2(g) 2SO 3(g) may be used) Sulphur dioxide and air pass over vanadium oxide catalyst at 450 o C Reaction is exothermic – reversible reaction, so excess air and SO 2 ensure good yield of SO 3

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g) 2. Preparation of sulphur oxide 2SO (s) + O 2(g) 2SO 3(g) 3. Preparation of sulphuric acid SO 3(s) + H 2 O (l)  H 2 SO 4(l)

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g) 2. Preparation of sulphur oxide 2SO (s) + O 2(g) 2SO 3(g) 3. Preparation of sulphuric acid SO 3(s) + H 2 O (l)  H 2 SO 4(l) 2 stages: (a) the sulphur oxide is dissolved in conc sulphuric acid to produce oleum ( b) The oleum is then diluted to give conc sulphuric acid which is 98% acid and 2% water

The Contact Process Three stage process. 1.Preparation of sulphur dioxide S (s) + O 2(g)  SO 2(g) 2. Preparation of sulphur oxide 2SO (s) + O 2(g) 2SO 3(g) 3. Preparation of sulphuric acid SO 3(s) + H 2 O (l)  H 2 SO 4(l) 2 stages: (a) the sulphur oxide is dissolved in conc sulphuric acid to produce oleum ( b) The oleum is then diluted to give conc sulphuric acid which is 98% acid and 2% water Sulphur oxide (SO 3 ) cannot be added to water directly since the reaction is violent and dangerous

Uses of sulphuric acid H2SO4 Fertilizers Synthetic fibres Car batteries Plastics Detergents DyesDrugsPaints

The Industrial Manufacture of Chemicals 1. The Haber Process - Ammonia, NH 3 2. The Contact Process – Sulphuric acid 3. Sodium hydroxide and Chlorine

“ describe the manufacture of sodium hydroxide and chlorine by the electrolysis of concentrated sodium chloride solution (brine) in a diaphragm cell ”

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water)

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine)

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side.

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl -

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl -

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl - 2Cl - - 2e -  Cl 2

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl - 2Cl - - 2e -  Cl 2 Chlorine gas

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl - 2Cl - - 2e -  Cl 2 Chlorine gas H 2 O  H + OH -

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl - 2Cl - - 2e -  Cl 2 Chlorine gas H 2 O  H + OH - H+H+

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl - 2Cl - - 2e -  Cl 2 Chlorine gas H 2 O  H + OH - H+H+ 2H + + 2e -  H 2

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Cl - 2Cl - - 2e -  Cl 2 Chlorine gas H 2 O  H + OH - H+H+ 2H + + 2e -  H 2 Hydrogen gas

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Chlorine gas H 2 O  H + OH - Hydrogen gas

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Chlorine gas H 2 O  H + OH - Hydrogen gas Na + + OH -  NaOH

Manufacture of sodium hydroxide and chlorine Sodium hydroxide, chlorine and hydrogen are all produced by the electrolysis of brine (salt – sodium chloride – dissolved in water) +- Titanium anode Steel cathode diaphragm Concentrated sodium chloride solution (brine) The diaphragm ensures that the products (hydrogen and chlorine) are kept separate – explosive!! The higher level of solution in the left hand cell ensures that the flow is always from the anode side to the cathode side. NaCl  Na + Cl - Chlorine gas H 2 O  H + OH - Hydrogen gas Na + + OH -  NaOH Sodium hydroxide solution

Uses of sodium hydroxide NaOH Manufacture of bleach Manufacture of paper Manufacture of soap Manufacture of chlorine Sterilising water supplies Manufacture of bleach Manufacture of hydrochloric acid

The Industrial Manufacture of Chemicals 1. The Haber Process - Ammonia, NH 3 2. The Contact Process – Sulphuric acid 3. Sodium hydroxide and Chlorine

End of Section 5 Lesson 4 In this lesson we have covered: The industrial manufacture of (1)Ammonia (the Haber Process) (2)Sulphuric Acid (the Contact Process) (3)Sodium hydroxide and Chlorine