Manufacture of ammonium sulfate fertiliser and phosphate fertiliser

Sulfuric acid reacts with ammonia to form ammonium nitrate according to the equation below. Ammonium nitrate is used as a fertiliser.

2NH₃(g)   +     H₂SO₄(aq)   =>   (NH₄)₂SO₄(aq)

Sulfuric acid converts insoluble calcium phosphate, in phosphate rock, to mixtures of soluble compounds that are available for plant uptake.  The mixtures are crushed and used as superphosphate fertilisers

Ca₃P(O₄)_2(s) + 2H₂SO_4(aq) +  4H_2(l)  =>  Ca(H₂PO₄)_2(s) + 2CaSO₄.2H₂O_(s)

The mixture of Ca(H₂PO₄)₂ and 2CaSO₄.2H₂O is known as superphosphate.

Dehydrating agent

Sulfuric acid is used as a drying agent in the manufacture of explosives, dyes and detergents and it brings about condensation reactions in the production of polymers, and esters

Concentrated sulfuric acid is used to remove the water from sugar according to the equation below.

C₁₁H₂₂O_11(s) => 12C_(s) + 11H₂O_(g)

Oxidising agent

Concentrated sulfuric acid is used as a strong oxidant. Depending on the temperature of the acid and the strength of the reductant we can obtain sulfur dioxide (SO₂), hydrogen sulfide (H₂S) or sulfur (S).

Zn_(s) + 2H₂SO_4(aq) => ZnSO_4(aq) + 2H₂O_(l) + SO_2(g)

Dilute sulfuric acid, like all other strong acids, forms hydrogen gas and a salt when it reacts with a metal, as shown on the right.

Zn_(s) + 2H₂SO_4(aq) => 2H_2(g) + ZnSO_4(aq)

Strong acid

Sulfuric acid acts as a diprotic acid, since under the right conditions, it can donate two protons.

Step 1- H₂SO_4(l) + H₂O_(l) ==> HSO₄^-_(aq) + H₃O⁺_(aq)

Step 2- HSO₄^-_(aq) + H₂O_(l) <==> SO₄^2-_(aq) + H₃O⁺_(aq)

Sulfuric acid is a strong acid and step 1 proceeds to completion. However step 2 is only partially completed.
The dilution of concentrated sulfuric acid produces an exothermic reaction. Sulfuric acid must always be added slowly to cold water when dilution is required. The danger of being splattered with sulfuric acid exists if water is added to sulfuric acid.

Its property as a strong acid is put to use in the cleaning of iron of surface oxide before it is galvanised.

Write the ionic equation to the reaction between sulfuric acid and iron oxide. The overall equation is shown below.

Fe₂O_3(s) + 3H₂SO_4(aq) => Fe₂(SO₄)_3(aq) + 3 H₂O(l)

solution.