Chapter 12 SULFUR

1. Sir. Muhammad Abdul Mageid
CIE - IGCSE Chemistry
Chapter 12 SULFUR
12.3 – Sulfuric Acid

2. Contents
12.2 –Sulfur dioxide
12.1- Sulfur – The element
12.3 – Sulfuric acid
Sir. Muhammad Abdul Mageid

3. Saturday, August 15, 2020
12.3 – Sulfuric acid
Sir. Muhammad Abdul Mageid
Manufacture of sulphuric acid
•Sulfuric acid is synthesized by the Contact process which use sulfur and
oxygen from air and is done in three distinct stages
Stage 1
•The first stage is the oxidation of sulfur:
𝑺 + 𝑶 𝟐 → 𝑺𝑶 𝟐
Stage 2
•The main stage is the oxidation of sulfur dioxide to sulfur trioxide using
V2O5 catalyst
𝟐𝑺𝑶 𝟐 + 𝑶 𝟐 ⇋ 𝟐𝑺𝑶 𝟐

4. 12.3 – Sulfuric acid
Sir. Muhammad Abdul Mageid
Conditions during Stage 2
Temperature: 450ºC
 The reaction is exothermic, so increasing the temperature shifts the position of
equilibrium to the left in the direction of the reactants
 Therefore the higher the temperature, the lower the yield of sulfur trioxide
 The optimum temperature is a compromise between a higher rate of reaction at a
higher temperature and a lower equilibrium yield at a higher temperature

5. Saturday, August 15, 2020
12.3 – Sulfuric acid
Sir. Muhammad Abdul Mageid
Pressure: 2 atm
 An increase in pressure shifts the position of equilibrium to the right in the
direction of a smaller number of gaseous molecules
 However the position of equilibrium lies far to the right (the equilibrium
mixture contains about 96% sulfur trioxide)
 So the reaction is carried out at just above atmospheric pressure because:
a) it is not worth spending the extra energy or money required to produce
high pressures
b) a higher pressure would increase the problems of dealing with the
corrosive mixture of gases

6. 12.3 – Sulfuric acid
Saturday, August 15, 2020
Sir. Muhammad Abdul Mageid
Stage 3
•Once stage 2 is completed, the sulfur trioxide is absorbed into a solution of
98% sulphuric acid to produce a thick liquid called oleum:
𝑺𝑶 𝟑 + 𝑯 𝟐 𝑺𝑶 𝟒 → 𝑯 𝟐 𝑺 𝟐 𝑶 𝟕
•It is not absorbed into water because a fine mist of sulfuric acid would be
produced and this would be difficult to condense and is also highly dangerous
•Oleum is added to water to form concentrated sulfuric acid:
𝑯 𝟐 𝑺 𝟐 𝑶 𝟕 + 𝑯 𝟐 𝑶 → 𝟐𝑯 𝟐 𝑺𝑶 𝟒

7. Properties of Sulfuric acid
Saturday, August 15, 2020
Sir. Muhammad Abdul Mageid
•Sulfuric acid is a strong dibasic acid as two of its hydrogen atoms can be
replaced by a metal
•It reacts in a similar way to other acids with metal carbonates, oxides,
hydroxides (and ammonia) and metals,
e.g:
𝑴𝒈 + 𝑯 𝟐 𝑺𝑶 𝟒 → 𝑴𝒈𝑺𝑶 𝟒 + 𝑯 𝟐
𝒁𝒏𝑶 + 𝑯 𝟐 𝑺𝑶 𝟒 → 𝒁𝒏𝑺𝑶 𝟒 + 𝑯 𝟐 𝑶
𝑵𝒂 𝟐 𝑪𝑶 𝟑 + 𝑯 𝟐 𝑺𝑶 𝟒 → 𝑵𝒂 𝟐 𝑺𝑶 𝟒 + 𝑯 𝟐 𝑶 + 𝑪𝑶 𝟐

8. Properties of Sulfuric acid
Saturday, August 15, 2020
Sir. Muhammad Abdul Mageid
 Concentrated sulphuric acid is corrosive and a powerful oxidising agent
 Concentrated sulphuric acid is also a very powerful dehydrating agent and
is very good at removing water from other substances
For example, if mixed with sugar (C6H12O6), concentrated H2SO4 will remove
water molecules and leave behind carbon in a spectacular looking reaction that
produces a tower of pure carbon

9. Properties of Sulfuric acid
Saturday, August 15, 2020
Sir. Muhammad Abdul Mageid
 Concentrated sulphuric acid is corrosive and a powerful oxidising agent
 Concentrated sulphuric acid is also a very powerful dehydrating agent and
is very good at removing water from other substances
For example, if mixed with sugar (C6H12O6), concentrated H2SO4 will remove
water molecules and leave behind carbon in a spectacular looking reaction that
produces a tower of pure carbon

10. Properties of Sulfuric acid
Saturday, August 15, 2020
Sir. Muhammad Abdul Mageid

11. Properties of Sulfuric acid
Sir. Muhammad Abdul Mageid

12. Uses of Sulfuric acid
Saturday, August 15, 2020
Sir. Muhammad Abdul Mageid
Dilute
 Used as a catalyst in many organic reactions
 Also used as to clean the surface of metals
Concentrated
 Used in car batteries,
making phosphate fertilisers, soaps and detergents
 It is also used to make acid drain cleaners and in the production
of paints and dyes