The p-Block Elements

Sulphuric Acid

You must have come across a lot of experiments with sulphuric acid. Haven’t you? So, is it ever put it in the water? NO! Never ever! But why? Let’s find out. In the following section, we will read all about sulphuric acid and its properties. After that, we will look at its uses. So let us first start with what it is.

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What is Sulphuric Acid?

Sulphuric acid also spelt as sulfuric acid or H2SO4 is an odourless, colourless, oily liquid. Also, it is very corrosive. Another name for it is Oil of Vitriol. On account of its wide applications, it has alluded as the ‘King of Chemicals’. Moreover, we can find it in both combined and free state.

sulphuric acid

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Manufacturing Process of Sulphuric Acid

In general, there are two techniques for industrial production of sulfuric acid. They are:

  • Lead chamber process
  • Contact process

Now, let us look at these processes in detail.

1) Contact Process

The contact process has three major steps.

  • Step – I: Production of Sulphur Dioxide

Sulphur dioxide is produced by heating sulphur or sulphide ores. For example, iron pyrites in excess of air.

S (Sulphur)   +   O2(Oxygen)   +   Δ(Heating)    →    SO2(Sulphur dioxide)

4FeS(Iron pyrites)   +   7O2(Oxygen)   +   Δ(heating)    →    2Fe2O3(Ferric Oxide)  +  4SO2(Sulphur dioxide)

  • Step -II: Formation of Sulphur Trioxide

Then sulphur dioxide is oxidized with atmospheric oxygen to sulphur trioxide by using V2O5 as a catalyst.

2SO2(Sulphur dioxide)   +   O2(Oxygen)   +   V2O5(Catalyst)   →    SO3(Sulphur trioxide)

  • Step -III: Conversion of Sulphur Trioxide into Sulphuric Acid

After that, the sulphur trioxide is broken in 98% sulfuric acid to give oleum. Another name for oleum is pyrosulfuric acid. Then  Oleum is diluted with water to give sulfuric acid of the desired concentration.

SO3(Sulphur trioxide)   +  H2SO4(Sulfuric acid-98%)    →    H2S2O7(Pyrosulfuric acid/Oleum)

H2S2O7(Pyrosulfuric acid/Oleum)    +  H2O(Dilution)    →     2H2SO4(Sulfuric acid)

2) Lead Chamber Process

The lead Chamber process is one of the most common manufacturing techniques. It results in around 50-60 B grade acids. In this process, we use wet SO2 in the presence of nitrogenous oxides (dynamic impetus). As a result, it gets oxidised with the oxygen in the air and forms sulphur trioxide. This reaction is expressed as

2SO2   +   O2    →   2SO3

Then sulphur trioxide is made to react with water to get H2SO4. This reaction is expressed as

SO3   +   H2O   →    H2SO4

Physical Properties of Sulphuric Acid

  • Sulfuric acid is a thick, colourless and an oily fluid.
  • It has a specific gravity of 1.84 at 298 K.
  • The boiling point of the acid is 611 K. The higher boiling point and thickness of this chemical is due to hydrogen bonding.
  • This strong chemical reacts with water vigorously releasing quite a lot of heat. Thus, you must never add water to H2SO4. Instead, you should add the acid to water, slowly with proper stirring.

Chemical Properties of Sulphuric Acid

  • Sulfuric acid is a strong dibasic acid. Also, it is diprotic and ionises in two stages in the aqueous solution.
  • This chemical is highly corrosive, reactive and is soluble in water. It has a very high oxidising power and thus, acts as a strong oxidising agent.
  • It has very low volatility. For this reason, it plays a part in the preparation of more volatile acids from their comparing salts.
  • Concentrated sulfuric acid is a very strong dehydrating agent. Thus, this chemical is used for drying many wet gases which do not react with the acid.
  • It additionally expels water from natural mixes like starches.
  • As it is a good oxidising agent, it can oxidise both non-metals as well as metals. Moreover, it itself reduces to sulphur dioxide.

Some Common Reactions of Sulphuric Acid

  • Hot concentrated sulfuric acid oxidizes copper to copper sulfate.

Cu   +    2H2SO4  →    CuSO +   SO2   +   H2O

  • Concentrated sulfuric acid gives out hydrogen chloride from sodium chloride. Also, it gives out hydrogen fluoride from calcium fluoride.

CaF2    +   H2SO4  →     CaSO  +  2HF

  • It burns glucose, sugar, and starch to carbon.

C12H22O11   +   (H2SO4)    →  12C   +  11H2O

Solved Example for You

Q: Write down the main uses of sulfuric acid.

Ans: The uses of sulfuric acid are:

  • It is a common chemical in the preparation of fertilizers. For example, ammonium sulfate and superphosphate.
  • We use it in the manufacture of dyes, shades, and paints.
  • It is a common chemical in the manufacture of explosives. For example, TNT.
  • Other imperative chemicals need the presence of sulfuric acid. Without sulfuric acid, we cannot get these chemicals. For example, hydrochloric, phosphoric and nitric acid. It is also needed for sodium carbonate.
  • We utilise it as a part of the refining of petroleum.
  • It acts as a pickling agent.
  • This chemical is common as a laboratory agent, dehydrating agent and an oxidizing.
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