CBSE Salt Analysis

Anions

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Group 1 :( Salt + Dil. H2SO4) -2 Colour/Odorless Gas with brisk effervescence – Carbonate(CO3 ) a. Aq. Sol + MgSO4 gives white ppt i. Na2CO3 + H2SO4 → Na2SO4 + CO2 + H2O ii. CO2 + CaOH → CaCO3 iii. Na2CO3 + MgSO4 → Na2SO4 + MgCO3 Colourless gas with bad/pungent smell, turns (CH3COO)2Pb(lead acetate) paper Black – Sulphide -2 (S ) a. Aq Sol + Sodium Nitroprusside gives violet colour i. Na2S + H2SO4 → H2S + NaSO4 ii. H2S + (CH3COO)2Pb → PbS(Black) iii. Na2S + Na2[Fe(CN)5NO] → Na4[Fe(CN)5NOS] -2 Colourless gas with pungent odour, turns K2Cr2O7 paper green - Sulphite (SO3 ) a. Aq. Sol + BaCl2 gives white ppt, soluble in conc. HCl i. Na2SO3 + H2SO4 → Na2SO4 + H2O + SO2 ii. SO2 + K2CrO7 + H2SO4 → K2SO4 + Cr2(SO4)3 + HCl iii. Na2SO3 + BaCl2 → NaCl + BaSO3 → BaCl2 + SO2 + H2O Brown fumes, treatment with dil. H2SO4 changes colour to orange - Nitrite (NO2 ) a. Aq. Sol + FeSO4 gives Black ppt i. NaNO2 + H2SO4 → 2HNO2 + Na2SO4 ii. 3HNO2 → H2O + NO2 + HNO3 iii. FeSO4 + NO → FeSO4NO Group 2 :( Salt + Conc. H2SO4) -) Pungent Smelling gas gives white fumes with rod dipped in NH4OH – Chloride (Cl a. Aq. Sol + AgNO3 gives white ppt, soluble in NH4OH b. Chromyl Chloride Test : Salt + Potassium Dichromate + conc. H2SO4 gives orange vapours on heating, NaOH vapours passed gives yellow solution, acetic acid + lead acetate added gives yellow ppt. i. NaCl + H2SO4 → HCl +NaHSO4 ii. HCl + NH4OH → NH4Cl iii. AgNO3 + NaCl → AgCl iv. AgCl + NH4OH → Ag(NH3)2Cl + H2O v. 2NaCl + K2Cr2O7 + 3H2SO4 → K2SO4 + Na2SO4 + 2CrO2Cl2 vi. CrO2Cl2 + 4NaOH → Na2CrO4 + 2NaCl + 2H2O vii. Na2CrO4 + (CH3COO)2Pb → 2 CH3COONa + PbCrO4 Brown Fumes, Do not intensify on adding Copper Turnings – Bromide (Br ) a. AgNO3 Test : Aq. Sol + AgNO3 sol. Gives creamy yellow ppt. partially soluble in NH4OH b. Layer Test : Aq. Sol + KMnO4 + conHNO3(1:4) shake well + CHCl3 → Yellow Layer i. NaBr + H2SO4 → NaHSO4 + HBr ii. 2HBr + O2 → Br2 + O2 iii. NaBr + AgNO3 → AgBr + NaNO3 iv. AgBr + NH4OH → Ag(NH3)2Br v. NaBr + Cl2 → 2NaCl + Br2 vi. Br2 + CCl4 → Yellow Layer Violet Fumes – Iodide (I ) a. AgNO3 Test : gives yellow ppt insoluble in NH4OH b. Layer Test : Violet Layer i. All of Br- except no iv Brown Fumes which intensify with addition of copper turnings (Without, barely visible) – Nitrate (NO3 )

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Ring Test : Aq. Sol + FeSO4 Drip conc. H2SO4 from the side of the test tube i. NaNO3 + H2SO4 → NaHSO4 + HNO3 ii. 4HNO3 (Heat) → 4NO2 + H2O + O2 iii. Cu + HNO3 → Cu(NO3)2 + 2NO2 + 2NO iv. FeSO4 + HNO3 + H2SO4 → FeSO4.NO Ring Test Colourless gas with vinegar like smell – Acetate (CH3COO ) a. FeCl3 + Aq. Sol → Blood Red Colour i. CH3COONa + H2SO4 → NaHSO4 + CH3COOH ii. CH3COONa + FeCl3 → (CH3COO)3Fe + NaCl 2-) Colourless, Odourless Gas, turns limewater milky – Oxalate (C2O4 Acidified KMnO4 + Na2C2O4 → Decolourises KMnO4 a. b. Aq. Sol + CaCl2 → White ppt. i. Na2C2O4 + H2SO4 → Na2SO4 + CO2 + H2O 2+ +2 ii. 5C2O4 + 2MnO4 + 16 H → 2Mn + 10CO2 + 8H2O iii. Na2C2O4 + CaCl2 → CaC2O4 + 2NaCl

Group 3: (Independent Group) 21. Sulphate (SO4 ) a. Aq. Sol. + BaCl2 (soln) gives a white ppt, insoluble in conc. HCl. i. Aq. Sol + (CH3COO)Pb + Acetic Acid → White ppt ii. Na2SO4 + BaCl2 → 2NaCl + BaSO4 iii. Na2SO4 + (CH3COO)2Pb → PbSO4 + CH3COONa 32. Phosphate ( PO4 ) a. Aq. Sol + HNO3 (conc), heat, add Ammonium Molybdate, heat again to give yellow ppt. i. Na3PO4 + 2HNO3 + 12(NH4)MoO4 → (NH4)3PO4.12MoO3 + 21NH4NO3 + 12H2O Cations 1.

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Zero Group + a. Salt + NaOH gives pungent smelling gas, white fumes with conc HCl rod – NH4 i. Aq. Sol + NaOH + Nessler’s Reagent → Brownish yellow ppt 1. NH4C2O4 + NaOH → NH3 + Na2C2O4 + H2O 2. NH3 + HCl → NH4Cl 3. NH4C2O4 + K2HgI4 → H2N – HgO – HgI2 + C2O4 Group 1 (OS + dil HCl) +2 a. White ppt, soluble in hot water – Lead (Pb ) i. Divide sol into 2 1. Add KI gives yellow ppt 2. Add K2Cr2O7 gives yellow ppt ii. Pb(NO3)2 + HCl → PbCl2 + HNO3 iii. PbCl2 + 2KI → PbI2 iv. PbCl2 + K2CrO4 → PbCrO4 + 2KCl Group 2 (Group 1 Sol, pass H2S) +2 a. Black ppt – Copper (Cu ) i. Add 50% HNO3 and heat. Add NH4OH in excess and divide 1. Divide sol into 2 parts a. CH3COOH and Potassium Ferrocyanide gives Chocolate Brown ppt b. CH3COOH and KI gives white ppt ii. CuS + HNO3 → Cu(NO3)2 +2 iii. Cu(NO3)2 + NH4OH → [Cu(NH3)4] (OH)2 +2 -2 iv. Cu + [Fe(CN)6] → Cu2[Fe(CN)6] +2 v. Cu + I → CuI2 +3 b. Yellow Solution – Arsenic (As )

i. Add 50% HNO3 and Ammonium Molybdate added to yellow solution which is heated strongly to give yellow ppt ii. As2S3 + HNO3 → 2H2AsO4 + 10NO2 + 3S + H2O iii. H2AsO4 + 12(NH4)MoO4 + 21 HNO3 → (NH4)3AsO4 + 12MoO4 + 21(NH4)NO3 + 12H2O 4.

Group 3 (add HNO3, boil off H2S add NH4Cl (solid), cool and add NH4OH in excess) +2 +3 a. Reddish Brown ppt – Ferrous/Ferric (Fe /Fe ) i. Filter ppt and dissolve in dil. HCl Divide into 3 parts 1. Add Ammonium Sulphocyanide/ Ammonium Thiocyanate →blood red colour 2. Add K4[Fe(CN)6] → Deep Blue Ppt 3. Add NaOH → white ppt ii. FeCl3 + 3NH4OH → Fe(OH)3 + 3NH4Cl iii. Fe(OH)3 + 3HCl → FeCl3 + 3H2O iv. FeCl3 + 3NH4SCN → Fe(SCN)3 + 3NH4Cl v. FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl +3 b. Gelatinous White ppt – Aluminium (Al ) i. Filter and dissolve in dil HCl. Add few drops of blue litmus and NH4OH in excess → Red solution with blue lake is formed ii. AlCl3 + 3NH4OH → NH4Cl + Al(OH)3 iii. Al(OH)3 + 3HCl → AlCl3 + 3H2O c. Divide solution into 3 parts

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Group 4 (Group 3 Solution, pass H2S gas) +2 a. Dirty White/Grey ppt – Zinc (Zn ) i. Filter and dissolve ppt in HCl. Divide into 2 1. Add K4[Fe(CN)6] → Greenish white ppt 2. NaOH → White ppt ii. ZnS + HCl → ZnCl2 + H2S(gas) iii. ZnCl2 + NaOH → Zn(OH)2 + 2NaCl iv. Zn(OH)2 + NaOH → Na2ZNO2 + 2H2O v. ZnCl2 + K4[Fe(CN)6] → Zn2[Fe(CN)6] + 4KCl +2 b. Buff ppt – Manganese (Mn ) i. Filter and dissolve ppt in HCl, add NaOH gives white ppt ii. MnS + 2HCl → MnCl2 + H2S iii. MnCl2 + 2NaOH → Mn(OH)2 + 2NaCl +2 +2 c. Black ppt – Ni /Co i. Filter ppt and dissolve in aqua regia, heat and divide into 2 parts +2 1. Add dimethylglyoxime and NH4OH solution – Cherry red ppt, Ni confirmed +2 2. Add NaOH – Sky blue/ Prussian Blue colour, Co confirmed Group 5 (Group 3 Sol + (NH4)2CO3) a. White ppt i. Dissolve in acetic acid and divide into 3 +2 1. Add K2CrO4 → Yellow ppt (Ba ) +2 2. Add (NH4)2SO4 → White ppt (Sr ) +2 3. Add Ammonium Oxalate → White ppt(Ca ) ii. All reactions are similar for Ba/Sr/Ca – check indi reactions for final iii. BaCl2 + (NH4)2CO3 → BaCO3 + NH4Cl iv. BaCO3 + CH3COOH → (CH3COO)2Ba + CO2 + H2O v. Barium (CH3COO)2Ba + K2CrO4 → CH3COOK + BaCrO4

vi. Strontium (CH3COO)2Sr + (NH4)2SO4 → 2CH3COONH4 + SrSO4 vii. Calcium (CH3COO)2Ca + (NH4)2C2O4 → 2CH3COONH4 + CaC2O4

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b. Alternatively, Flame test can be used i. Take a Platinum Wire/Glass Rod dipped in conc. HCl and rub in salt. Place in Flame +2 1. Apple green Flame → Ba +2 2. Sparkling Red Flame → Sr +2 3. Brick Red Flame → Ca Group 6 (Group 3 + (NH4)2HPO4 Ammonium Orthophosphate) 2+ a. White ppt – Mg i. MgCl2 + NH4OH + (NH4)2HPO4 → MgNH4PO4 + 2NH4Cl + H2O TIPS If Phosphate Anion is present, Group 1 and V of Cation is absent Anion If Ammonium is present is oxalate If Lead is present, anion is either nitrate or oxalate, If nitrate is suspected, heat and hear a cracking noise +2 If Sulphate is detected, Barium, Calcium, Lead and Sr are absent Probability of Arsenic/ Nickel/Cobalt is very low since aq sol has to be given Nitrates, Nitrites, Acetates, Carbonates (Alkali Metal and NH4) are water soluble, rest dissolve in Dil. HCl If OS is prepared in Dil HCl Group 1 is absent [quite obviously] Colour can give ideas a. Pink – Manganese b. Blue – Copper c. Deep Yellow/large granule size – Magnesium (Suspect to be wrong), Mg salts tend to look wet.