FeSO4 solution mixed with (NH4 ) 2 SO4 solution in 1 : 1 molar ratio gives the test of Fe2+ ion but CuSO4 solution mixed with aqueous ammonia in 1 : 4 molar ratio does not give the test of Cu2+ ion. Explain why ?
When FeSO4 and (NH4 ) 2 SO4 solution are mixed in 1 : 1 molar ratio, a double salt is formed. It has the formula FeSO4 (NH4 ) 2 SO4 . 6 H2O. In aqueous solution, the salt dissociates. When CuSO4 and NH3 are mixed in the molar ratio of 1 : 4 in solution, a complex [Cu (NH3 ) 4 ] SO4 is formed.