Lab 8 Cations Scheme PDF

LAB 8 CATIONS SCHEME All Cations  Ag+ ,Pb2+  Cd2+ ,Cu2+ ,Bi3+  Fe3+ ,Cr3+ ,Al3+  Zn2+ ,Mn2+ ,Co2+ , Ni2+  Ba2+ ,Sr2+ ,Ca2+ Steps of scheme Step I Step II Step III Step IV Step V Step I: Unkn. + dil. HCl White ppt (Gp I)...

LAB 8 CATIONS SCHEME All Cations  Ag+ ,Pb2+  Cd2+ ,Cu2+ ,Bi3+  Fe3+ ,Cr3+ ,Al3+  Zn2+ ,Mn2+ ,Co2+ , Ni2+  Ba2+ ,Sr2+ ,Ca2+ Steps of scheme Step I Step II Step III Step IV Step V Step I: Unkn. + dil. HCl White ppt (Gp I) No ppt step 2 Take new sol. + KI Bright yellow ppt. therefore, it’s Pd2+ Pale yellow ppt. Confirm: Therefore , its new sol. + K2CrO4 yellow ppt of PbCrO4 silver Ag+ new sol. + dil H2SO4 white ppt of PbSO4 Confirm: New sol. +K2CrO4 Brick red ppt Ag2CrO4 Step II: Unkn + dil. HCl + Xss H2S PPT No PPT Therefor , group II step III Yellow ppt. Black ppt Therefor; Cd+2 Therefor; Cu+2 or Bi +3 *New sol. +conc. NH4OH Intense blue. White gel ppt. Therefore; Cu+2 Therefor; Bi +3 Confirm: Confirm: Add to blue color acetic acid till pale blue Add to white gel alkaline then add ferrocyanide chocolate stannite Black ppt. brown ppt. Cu2 [Fe(CN)6] Step III: Unkn +NH4CL (Solid)+Conc. NH4OH PPT No PPT step IV Therefor , group III Reddish Dirty green White gel brown ppt. ppt. Therefor, Therefor, Therefor, Al+3. Fe+3. Cr+3. In case of Fe+3 : Confirm1: New sol.+ K.Ferrocyanide Prussian blue ppt. Confirm2: New sol. + ammonium thiocyanate blood red complex. In case or Cr+3 & Al+3 Take the residue + 10% xss NaOH + 3 dps H2O2 Boil till no O2 evolve (no bubbles) Yellow solution may be Colorless sol. Cr+3 confirm: May be Al+3 Add on yellow solution Acetic acid + On the colorless Lead Acetate sol. Add Excess NH4Cl(Solid) Yellow ppt of Boil PbCrO2 + Cool White gelatinous ppt of Al(OH) 3 Step IV Unknown+ add conc.NH4OH + solid NH4Cl +H2S Residue (ppt) No ppt Therefore, (Gp IV) Maybe (group V-VI) White (Zn2+) Buff (Mn2+) Black (Co 2+ or Ni 2+) Confirm: If ppt buff: soln+ 10%NaOH+ 2dps H2O2 brown ppt. (Therefore Mn 2+ ) If ppt white: soln +NaOH White ppt Xss NaOH dissolve H S 2 white ppt Zn2+  If black ppt New Sol + NH4Cl solid+ Conc NH4Cl +D.M.G Rose Red -ve Therefore, it’s Ni2+ test for Co2+ new Sol.+ xxs ether+ solid NH4SCN blue in ether layer Therefore, it’s Co2+ Step V Unknown + 10% NH4Cl+ Conc. NH4OH+ (NH4)2 CO3 White ppt -Ve Therefore, it’s Gp V (repeat from the beginning) Do the following in order: Test for Ba2+ : soln+ K2CrO4 Canary Yellow ppt Test for Sr2+ : Soln+ (NH4) 2SO4 White ppt In case any test gave +ve don’t perform the rest Test for Ca2+ : Soln+ NH4 Oxalate White ppt