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by Admin PH Mohamed Hamdy Analytical chemistry lecture (2) lecturer:Dr.Magda Hello everybody let’s start but at first there is summary for lecture (1) ↓↓ HCO3ˉ Test CO3ˉ ˉ Dry Reactions Solid+dil.Hcl Then warm eff with evolution of colorless gas (CO2↑), which cause turbidity to limewater and disappear after prolonged time Wet Reactions (1)AgNo3 White ppt og Ag2No3 -soluble in HNo3,Amonia -Turn Brown if boiled White ppt of Baco3 White ppt of Caco3 White ppt of MgCo3 - sol. In mineral acids (2) Bacl2 Cacl2 MgSo4 No PPt on cold ↓∆ Give ppt No PPt on cold ↓∆ Give ppt Some notes - Dr.Magda canceled spot test -*(star) means positivecharge (+) in the slides Sulphur containing Anions:1-Sulphur Sˉˉ 2-Sulphide SO3ˉˉ 3-Thiosulphate S2o3ˉˉ 4-Sulphate SO4ˉˉ 5-persulphate S2O8ˉˉ sˉˉ,SO3ˉˉ,S2O3ˉˉ are reducing agents can react with oxidizing agents like →K2Cr2O7 pot.di chromate → KMno4 pot.permenganate (1) Sulphide Sˉˉ :- Parent Acid:- H2S (weak acid) H2S ↔ H* + HS ˉ ( hydro sulphide) HS ˉ↔ H*+ Sˉ(Sulphide ) Dry Test :- (Actions of Dil.Hcl ) -Sˉˉ + 2H*→H2S gas ↑↑ or Na2S + 2HCl → H2S ↑↑ + 2 NaCl H2S can be Detected by :1-gas with offensive rotton egg odour رائحة البيض الفاسد 2-It can Blacken filter paper moisted with leadacetate Pb(Ac)2 Pb(Ac)2 + H2S → PbS ↓↓ Black ppt Pb** + H2S →PbS ↓↓Black ppt Wet Reactions : - Reactions with BaCl2:- ( - ve ) -Reactions with AgNO3(Silvernitrate): Sˉˉ + 2Ag* → Ag2S ↓↓ Black ppt which is soluble in Dil.HNO3 , Insoluble in Ammonia and KcN -Reactions with Pb(Ac)2 :Sˉˉ + Pb** → PbS ↓↓ Black ppt -Reactions with FeCl3:3Sˉˉ + 2F*** → Fe2S3 ↓↓Black ppt ( Soluble in dil.Acids like dil.HCl) (2) Sulphite SO3ˉˉ :- Parent Acid :H2SO3 Sulphurous Acid weak acid ( easily decomposed) - Dry Test :SO3ˉˉ+ 2H* →H2SO3→H2O+SO2↑ SO2 Can be detected by the following :1- It has Burnt Sulphur odour 2- cause Turbidity to limewater SO2 + Ca(OH)2→CaSO3↓↓+ XSS SO2 → Ca(HSO3)2 (soluble ) Note : Sulphite Has Reducing properties Cr2O7ˉˉ + 2 H* + SO2 → SO4ˉˉ + 2Cr*** (green colour )+ H2O (-)Wet Reactions :-Reaction with BaCl2 :SO3ˉˉ + Ba** →BaSO3 ↓↓( white ppt sol. In dil HCl ) BaSO3 + [O]→ BaSO4↓↓(white ppt which is insol. In dil HCl ) - Reaction with AgNO3 :2Ag* + SO3ˉˉ → Ag2SO3↓↓ ( white ppt ) Ag2SO3 (Δ)→2Ag˚↓↓ +Ag2SO4+SO2↑ ( Grey or black ppt ) Note : Silver sulphite Is soluble in HNO3, Ammonia but excess sulphite give acomplex whichon boiling give grey ppt of mettalic Ag˚ Ag2SO3 + SO3 (xss) →2[Ag(SO3)2]ˉˉˉ(boiling)→2Ag˚↓+ Ag2SO4 + SO2 ↑ (grey or black ppt ) -Reaction with Pb(AC)2:Pb** + SO3ˉˉ →PbSO3↓↓ + [O] →PbSO4 ↓↓ ( PbSO3 is white ppt which is soluble in cold HNO3 and on boiling oxidised to PbSO4 ) -Reaction with FeCl3 :2Fe** + 3SO3ˉˉ → Fe(SO3)2 (Red complex) Fe(SO3)2(Δ)→Reddish Brown ppt of Basic iron salt System of exam questions (1)- By equation only : what is the effect of silver nitrate or FeCl3 on ( Sˉˉ , SO3ˉˉ,S2O3ˉˉ, SO4ˉˉ ) (2)- Write By equation the effect of HCl on ( Sˉˉ,SO3ˉˉ,S2O3ˉˉ, SO4ˉˉ) As you see it is big lecture this is nearly half of it I hope it can be useful for you so at last thanks for god God willing,the second half will be soon PH Mohamed Hamdy