REACTIONS OF GROUP IV CATIONS 1. Reactions of Zinc, Zn2+ Zinc sulphide is precipitated A white precipitate is obtained . 1. To a little of the salt solution am- monium chloride and excess of ammonium hydroxide are added and hydrogen sulphide is passed through it. Zinc hydroxide formed is soluble 2. To a little of the salt solution A white precipitate soluble in in excess of NaOH. NaOH solution is added drop by excess of NaOH is formed. ZnSO4 drop till in excess. Zn(OH)2 + 2NaOH-> Na,ZnO2+2H2O 3. Ash test : About 2ml of the salt Green colour is formed to the Green ash is obtained solution is boiled with one or two formation of double oxide of drops of conc.HNO, and a few cobalt and zinc. drops of cobalt nitrate . A filter paper dipped in it is burnt to ashes 2. Reactions of Manganese , Mn2 A pink or flesh coloured precipi- Manganese sulphide is pre- 1. To a little of the salt solution NH4C CI and excess of NH2OH are tate cipitated MnCl,+H,S-MnS + 2HCI. added and H,S is passed through it. Mn(OH)2 formed on exposure 2. To a little of the salt solution A white precipitate which turns to air oxidised to Mn(OH)3 - NaOH solution is added drop by brown on keeping MnCl2+2NaOH-Mn(OH)2+2NaC drop till in excess 4Mn(OH),+O,+2H,O -4Mn(OH), 3. Permanganic acid test A little of This is due to the formation of The supernatent liquid gets a the salt is boiled with conc. HNO 3 permanganic acid pink colour and a pinch of lead peroxide It is 5PbO2 + 10HNO1 +2Mn2 then diluted with water and allowed 2HMnO,+10Pb(NO,)2 to remain for a while. +2H,O+4H+
3. Reactions of Cobalt ,Co2+ 1. To a little of the salt solution am- A black precipitate Cobalt sulphide is precipitated monium chloride and ammonium .Co(NO)2 +H,S hydroxide are added and H2S is CoS + 2HnO passed - 2. To a little of the sallt solution A reddish brown precipitate is Cobalt ferricynaide is fromed . NH2OH 4 and pottassium obtained . 3CoCl2 + 2K,[Fe(CN),] ferricynaide solutions are added . Co3[Fe(CN),J2 + 6KCI 4. Reactions of Nickel ,Ni2 1. To a little of the salt solution A black precipitate. . Nickel sulphide is precipitated NiCl+H2S NiS+2HCI. NH2C1 and excess NH OH are added and H2S passed through it . 2. To a little of the salt solution am- A rose red precipitate Nickel dimethyl gloxime is pre- monium hydroxide and dimethyl cipitated gloxime are added.