P-1 Heat — Science STD 10 — Question

(a) When iron powder is added to the blue coloured copper sulphate solution, the iron ions formed from iron atoms take the place or $Cu ^{2+}$ ions in $CuSO _4$, and copper atoms, formed from $Cu ^{2+}$ ions comes out i.e. the more reactive iron displaces the less reactive $Cu$ from copper sulphate. Therefore this reaction is a displacement reaction.
(b) The reaction in which the place of the ion of a less reactive element in a compound is taken by another more reactive element by formation of its own ions, is called displacement reaction.