Chapter : 1. Metals & Non Metals
Action of acids / Features
4. Action of acids : Iron lies above hydrogen in the activity series of metals. So, it can displace hydrogen from dilute hydrochloric acid or dilute sulphuric acid. The corresponding ferrous salts are also produced.
(i) With hydrochloric acid
(a) Iron dissolves in dilute hydrochloric acid, forming ferrous chloride with the evolution of hydrogen gas.
Fe + 2HCl → FeCl2 + H2
(b) Concentrated hydrochloric acid also produces hydrogen with iron.
(ii) With sulphuric acid
(a) Iron dissolves in dilute sulphuric acid, forming ferrous sulphate. Hydrogen gas is evolved in the reaction.
Fe + H2SO4 → FeSO4 + H2
(b) Iron reacts with concentrated sulphuric acid to form ferrous sulphate with the evolution of sulphur dioxide. Hydrogen gas does not evolve in this reaction.
Fe + 2H2SO4 → FeSO4 + SO2 + 2H2O
Some ferric sulphate is also formed due to the oxidation of FeSO4 by concentrated H2SO4.
2FeSO4 + 2H2SO4 → Fe2(SO4) + 2H2O + SO2
(iii) With nitric acid :
(a) Iron reacts with dilute nitric acid to form ferrous nitrate and ammonium nitrate.
4Fe + 10HNO3 → 4Fe(NO3)2 + NH4NO3 + 3H2O
(b) With concentrated nitric acid, iron is rendered passive due to the formation of insoluble ferrosoferric oxide (Fe3O4) on the surface of iron.
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