Sulphur is a non metal element in group 6 of the periodic table. Sulphur has many useful properties which make it widely used in the industry.
Sources of Sulphur:
Sulphur is found in many places in the world in different forms. It usually exists in volcanic regions in USA, Mexico and Sicily. Sulphur could also be obtained from some metal ores like Copper pyrites (CuFeS2) and Blende (ZnS).
Properties of Sulphur:
In room temperature, sulphur is a yellow, brittle solid which doesn’t conduct electricity as it is a non-metal. Sulphur is insoluble in water. It is able to react with both metals and non-metals.
Sulphur dioxide is the product of combustion of sulphur or sulphur-containing fuels. As you have studied in the previous chapter, it is an air pollutant as it causes acid rain. However, SO2 has important uses too:
- Bleaching wood pulp for the manufacturing of paper
- It is used as a food preservative as it kills bacteria
- Manufacturing of Sulphuric acid
Contact Process (Manufacturing of Sulphuric Acid):
Sulphuric acid is one of the most important chemicals in the industry since it has a role in the manufacturing of almost every product. Sulphuric acid is manufactured by a process called Contact Process and it involves several steps:
- Making the sulphur dioxide
- Converting the sulphur dioxide into sulphur trioxide
- Converting the sulphur trioxide into sulphuric acid
1. Making the sulphur dioxide
Sulphur is first burned in air producing sulphur dioxide:
S(s)+ O2(g)→ SO2(g)
2. Converting the sulphur dioxide into sulphur trioxide:
This is a reversible reaction, and the formation of the sulphur trioxide is exothermic.
2SO2(g) + O2(g) ⇌ 2SO3(g)
3. Converting the sulphur trioxide into sulphuric acid
This can't be done by simply adding water to the sulphur trioxide - the reaction is so uncontrollable that it creates a fog of sulphuric acid. Instead, the sulphur trioxide is first dissolved in concentrated sulphuric acid:
H2SO4(l) + SO3(g) → H2S2O7(l)
The product is known as fuming sulphuric acid or oleum.
This can then be reacted safely with water to produce concentrated sulphuric acid - twice as much as you originally used to make the fuming sulphuric acid.
H2S2O7(l) + H2O(l) → 2 H2SO4(l)
The average percentage yield of this reaction is around 30%.
Properties & Uses of Sulphuric Acid:
Sulphuric acid is a very strong acid. It is a dibasic acid which means it every molecule of it produces two hydrogen ions when it is dissolved in water. Sulphuric acid has some other unique properties. For example, it is a dehydrating agent. This means it eliminates water from compounds.
|E.g.: CuSO4.5H2O||CuSO4 + 5H2O|
|E.g.: C6H12O6||6C + 6H2O|
It is also a drying agent. This means it removes water from mixtures. Don’t confuse that dehydrating agent.