REACTION OF ZERO GROUP CATION Reactions of Ammonium NH4+ 1. Action with Na2CO : No precipitate. Ammonium carbonate formed is soluble in water. A little of Na2CO3 solution is 2NH2C + Na,CO 2NaCl added to an aqueous solution of +(NH))CO,(soluble) ammonium salt. 2. To an aqueous solution of the Colourless gas with the smell NaOH decomposes ammonium salt, a little NaOH solution is of ammonia. salt into ammonia. added. NH2CI + NaOH NaCI + NH,+HLO 3. A glass rod dipped in conc. HCI Dense white fumes This is due to the formation of is shown to the above gas. ammonium chloride. NH1 + HCI NH2CI 4. To a little of the solution The precipitate is due to the formation A brown precipitate is formed. Nessler's reagent is added. of mercuric amino iodide, NH,Hg,L
REACTION OF GROUP I CATION Reactions of Lead Pb2+ Lead chloride is precipitated. 1. To a little of the salt solution dil. A white precipitate formed is HCI is added. Pb(NO)2 2HCI soluble in hot water. PbCl2 + 2HNO, PbCl2 is soluble is hot water. 2. To the salt solution potassium Yellow precipitate soluble in Lead iodide is precipitated. iodide solution is added. hot water but reappears as Pb(NO,),+2K1 - 2KNO,+ golden spangles on cooling. Pbl, 3. To the salt solution acetic acid Yellow precipitate. Lead chromate is precipitated. and potassium chromate solution Pb(NO)2 +K,CrO are added. PbCrO4 I 2KNO3 REACTION OF GROUP II CATIONS 1. Reactions of Copper, Cu2+ 1. To a little of the salt solution dil. A black precipitate. Copper sulphide is precipitated. HCI is added and then H,S gas CuSO 4+H H2SO4 + is passed. CuS 2. To a little of the salt solution A pale blue precipitate soluble The Cu(OH)2 precipitate is NH OH is added drop by drop in excess of NH2OH to give soluble in excess of NH2OH. till in excess. a deep blue solution. CuSO,+2NH,OH Cu(OH), + Cu(OH)2+4NH [Cu(NH,),](OH), 3. To a little of the salt solution A chocolate brown precipi- This is due to the formation of acetic acid and potassium fer- tate is formed. copper ferrocyanide. rocyanide solution are added. 2CuSO,+[K,[Fe(CN),] 2. Reactions of Cadmium, Cd2+ 1 Hydrogen sulphide is passed A yellow precipitate is The yellow precipitate is cad- through a slightly acidic (dil. formed. mium sulphide. HCI) solution of cadmium salt. 2. To a little of the salt solution A white precipitate soluble in ammonium hydroxide is added Cd(OH)2 + formed is soluble in excess of NH2OH is formed. drop by drop till in excess excess of NH,OH.
CdSO4 +2NH2OH Cd(OH), +(NH2) SO [Cd(NH,),SS,+ 2H2O 3. Hydrogen sulphide is passed A yellow precipitate is ob- Cadmium sulphide is precipi- through the above solution. tained tated. 3. Reactions of Arsenic As3+ 1. A little of the salt solution is A yellow precipitate is Arsenic sulphide is precipitated acidified with dil. HCI and hy- formed. 2AsCl3 + 3H,S drogen sulphide is passed As2S, + 6 HCI through it. 2. The above precipitate sepa- Precipitate dissolved. Ammonium arsenite formed is rated, washed and then warmed soluble. with ammonium carbonate so- lution. 3. The above solution is acidified A yellow precipitate is This is due to the formation of with dil. HCI formed. arsenic sulphide.