CHAPTER 9: MANUFACTURED SUBSTANCES IN INDUSTRY

Sulphuric Acid

Name: Muhd Iqbal bin Husni Nizad Nurul Shyazwani bt. Ramdzan Nurain Nasuha bt. Tajul Arafat

Class : 4K1

Instructor: En. Mohd Nor b. Latif

GENERAL

Sulphuric acid is a highly corrosive strong mineral acid The molecular formula for sulphuric acid is HSO Sulphuric acid, is a non-volatile diprotic acid Concentrated sulphuric acid is a viscuos colourless liquid.

Manufacture of sulphuric acid is one of the most important chemical industries in the present time.

USES OF SULPHURIC ACID

1. Manufacture of fertiliser Calcium dihydrogen phosphate (super-phosphate) [reaction

between sulphuric acid and tricalcium phosphate]

Ammonia sulphate [reaction between sulphuric acid and aqueous ammonia]

Potassium sulphate [reaction sulphuric acid between potassium hydroxide]

2. Manufacture of detergents (synthetic cleaning agents) Sulphuric acid reacts with hydrocarbon to produce sulphonic

acid. Sulphonic acid is then neutralised with sodium hydroxide to

produce detergent.

3. Manufacture of synthetic fibres (polymers) Example : Rayon Produce by reaction between sulphuric acid on cellulose.

4. In school laboratory Strong acid Drying or dehydrating agent Oxidising agent Sulphonating agent Catalyst

5. Manufacture of white pigment in paint barium sulphate, Neutralisation between sulphuric acid and barium hydroxide

produces Barium sulphate.

MANUFACTURE OF SULPHURIC ACID

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1.Sulphuric acid is manufactured by the Contact process in industry.2.The raw materials used in the Contact process are sulphur (or sulphide minerals), air and water.3. This process contains three stages.

Production of Sulphur Dioxide from Sulphur

Production of Sulphuric Acid from Sulphur Trioxide

Conversion of Sulphur Dioxide to Sulphur Trioxide

Sulphur or metal sulphide

Sulphur dioxide, SO₂

Sulphur trioxide, SO₃

Concentrated sulphuric acid, H₂SO₄

Oleum, H₂S₂O₇

burned in air

(i) V₂O₅ as the catalyst(ii) Temperature of 450⁰ C- 550⁰ C(iii)Pressure of 1 atmosphere

Dissolved in concentrated H₂SO₄

Diluted with equal volume of H₂O

STAGE 1 STAGE 2STAGE 3

STAGE1: Production Of Sulphur Dioxide From Sulphur

i. Combustion of sulphur or sulphide ores in the air produce sulphur dioxide, SO₂

S + O₂ SO₂

This can be done by two methods:

1.Burning of sulphur in dry air in the furnace

S + O₂ SO₂

2. Burning of metal sulphide such as zinc sulphide or iron(III) sulphide in dry air.

2ZnS + 3O₂ 2SO₂ + 2ZnO

STAGE 2: Conversion of Sulphur Dioxide, SO₂ to Sulphur Trioxide, SO₃

1. The sulphur dioxide gas, SO ₂ is dried and purified before being added to dry air to produce sulphur trioxide gas, SO₃.

2. Under controlled optimum conditions, 98% conversion is possible. Sulphur dioxide and oxygen that have not reacted are allowed to flow back again over the catalyst in the converter

3. The optimum conditions are1. a)Temperature of between 450-500°C 2. b)Pressure of 1 atmosphere3. c)Catalyst: Vanadium(V) oxide

STAGE 3: Production of Sulphuric Acid from Sulphur Trioxide

1. In the absorber, sulphur trioxide, SO₃ is dissolve in concentrated sulphuric acid to produce oleum, H₂S₂O₇, a viscous liquid.

SO₃ + H₂SO₄ H₂S₂O₇

2. Then, the oleum is diluted with an equal volume of water to produce concentrated sulphuric acid (98%)

H₂S₂O₇ + H₂O 2H₂SO₄

3. The two reactions in this stage are equivalent to adding sulphur trioxide, SO₃ to water, H₂O

SO₃ + H₂O H₂SO₄

OUTLINE OF CONTACT PROCESS

SULPHUR DIOXIDE AND ENVIROMENTAL

POLLUTION

SULPHUR DIOXIDE Sulphur dioxide is present to some extent in the natural unpolluted air and

is considered non-polluting as it is of low concentration. They come from: -bacteria decay of organic matter

-volcanic gases

-forest fires Sulphur is found in coal and petroleum. When they are burnt, they

produce sulphur dioxide.S(s) + O2(g) SO2(g)

When they are released into the atmosphere, they pollute the air.

In fact, the burning of coal and oil is the major source of sulphur dioxide pollution in our environment. This gas is considered as the most serious health hazard among the pollutants. This is true especially for people with respiratory difficulties.

The release of sulphur dioxide gas to the atmosphere can be reduced by reacting the gas with :

(a) calcium carbonate

SO2(g) + CaCO3(s) CaSO3(s) + CO2(g)

(b) calcium oxide

i) CaO(s) + SO2 CaSO3(s)

ii) 4CaO(s) + 4SO2(g) +2O2(g) 4CaSO4(g)

Acid rain Acid rain happens when:

SO₂ dissolves in water or rain,

they form sulphurous acid

H₂SO₃

Atmospheric SO₂ can also be

oxidised to SO₃. When SO₃

dissolves in water,it forms sulphuric acid

H₂SO₄

Acid rain

CO₂ dissolves in water to form carbonic acid

H₂CO₃

ACID RAIN AND ENVIRONMENTAL POLLUTION

Bad effects of acid rain

1. Damage marble structuresa) The chemical compound in marble is calcium carbonate.b) The acid rain reacts with calcium carbonate to release carbon dioxide.

CaCO₃(s) + 2H+(aq) Ca₂+(aq) + CO₂(g) + H₂O(l)

2. Damage to metal structures a) All acids react with active metals such as aluminium, iron and zinc.

Fe(s) + 2H+(aq) Fe₂+(aq) + H₂(g)b) Therefore acids increase the rate of corrosion of meal structures.

3. Threat to aquatic lifea) Aquatic animals generally live in water with pH range of 6.5 to 8.4b) Acid has the pH of 0 to 6.9. Therefore acid will decrease the pH of the water. This will not help the survival of fish and other aquatic life.

4 Damage to the soil nutrients of plantsa) Acid rain dissolves minerals in the soil to form soluble compounds such as sodium salts, calcium salts and aluminium salts.b) Many of these salts are soluble in water. When these dissolved salts are washed away by acid rain, the plant will not have enough nutrients to survive.

REDUCING ACID RAIN

1. Acid rain can be reduced by reducing all the sources of the acid. (refer slide 4)

2. Sulphur dioxide can be removed directly by reacting them with calcium carbonate.CaCO3(s) + SO2(g) CaSO3(s) + CO2(g)

The calcium sulphite reacts with the oxygen in the air to form calcium sulphate.

2CaSO3 (s) + O2(g) 2CaSO4(s)

3. Another chemical that can be used to react with sulphur dioxide is calcium oxide.CaO(s) + SO2(g) CaSO3(s)2CaSO3(s) + O2 2CaSO4(s)

REDUCING THE ACIDITY IN THE SOIL, RIVERS AND LAKES

1. The acidity in these areas can be reduced with the following chemicals.

a)Calcium oxide CaO(s) + 2H(aq) Ca(aq) + H2O(l)

b) Calcium hydroxideCa(OH)2(s) + 2H(aq) Ca(aq) + 2H2O(l)

c) Calcium carbonateCaCO3(s) + 2H(aq) Ca(aq) + H2O(l) + CO2(g)

2. The chemical can be spread in the soil so that the acid will be neutralised.