Thursday, 19 February 2015

9.1 Manufacture of Sulphuric Acid

Sulphuric acid
■ Sulphuric acid

A non-volatile diprotic mineral acid with the molecular formula H2SO4

A pungent, colorless viscous liquid which is soluble in water at all concentrations.

One of the most important chemical industries.
■ This video contains information on the uses of sulphuric acid

Uses of sulphuric acid
■ Uses of sulphuric acid
Synthetic fibre
Paint pigments

Manufacture of sulphuric acid in industry
■ Sulphuric acid

Sulphuric acid

Raw materials used to manufacture the sulphuric acid are sulphur, air and water.
■ This video contains information on the syntheis of sulphuric acid through the Contact process in industry.

■ Contact Process

Stage I: Production of sulphur dioxide gas, SO2
Sulphur dioxide gas, SO2, is produced by burning sulphur in air.
S(s) + O2(g) → SO2(g)

Stage II: Conversion of sulphur sulphide to sulphur trioxide, SO3
Pure and dry sulphur dioxide with excess oxygen are passed through a converter.
The gas mixture is passed over vanadium(V) oxide, V2O5 (catalyst) at temperature 450°C – 500°C and under the pressure of 1 atmosphere.
A high percentage of the sulphur dioxide is converted into sulphur trioxide.
2SO2(g) + O2(g) ⇌ 2SO3(g)

Stage III: Production of sulphuric acid, H2SO4
The sulphur trioxide produced is dissolved in concentrated sulphuric acid to produce oleum, H2S2O7, a viscous liquid.
SO3(g) + H2SO4(l) → H2S2O7(l)
Oleum is then diluted with an equal volume of water to produce concentrated sulphuric acid (98%).
H2S2O7(l) + H2O(l) → 2H2SO4(l)

The animation below shows the industrial process in the manufacture of sulphuric acid.
■ This video contains information on the manufacture of sulphuric acid in industry.

Environmental pollution by sulphur dioxide
■ Sources of sulphur dioxide:

Volcanoes eruptions.

Waste gases from various industrial process.

Burning of fossil flues such as petroleum and coal.
■ Effects of sulphur dioxide in air:

Sulphur dioxide is a poisonous and acidic gas.

It can diffuse into our respiratory system and cause diseases such as bronchitis, asthma and lung infections.
■ Acid rain:

Sulphur dioxide gas dissolves in atmospheric water to produce a mixture of sulphurous acid, H2SO3 and sulphuric acid, H2SO4.
SO2 + H2O → H2SO3
2SO2 + O2 + 2H2O → 2H2SO4

Both acids presence in rainwater results in acid rain.

The animation below shows the formation of acid rain.
■ Effects of acid rain:

Increase the metal corrosion speed.

Results in highly acidic soil which is not conducive for agriculture activities.

Cause the destruction of concrete buildings.

Lower the pH value of water in river and seas.

Destroy the nutrients in the soil.

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