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by Admin PH Mohamed Hamdy

by Admin PH Mohamed Hamdy. I am proud to be pharmacist. Analytical chemistry lecture (2) lecturer:Dr.Magda. Hello everybody let’s start but at first there is summary for lecture (1) ↓↓. Some notes - Dr.Magda canceled spot test -*(star) means positivecharge (+) in the slides .

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by Admin PH Mohamed Hamdy

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  1. by AdminPH Mohamed Hamdy I am proud to be pharmacist

  2. Analytical chemistrylecture (2)lecturer:Dr.Magda

  3. Hello everybody let’s startbut at first there is summary forlecture (1) ↓↓

  4. Some notes - Dr.Magda canceled spot test-*(star) means positivecharge (+) in the slides 

  5. Sulphur containing Anions:-1-Sulphur Sˉˉ2-Sulphide SO3ˉˉ3-Thiosulphate S2o3ˉˉ4-Sulphate SO4ˉˉ5-persulphate S2O8ˉˉ

  6. sˉˉ,SO3ˉˉ,S2O3ˉˉ are reducing agents can react with oxidizing agents like →K2Cr2O7 pot.di chromate→ KMno4 pot.permenganate

  7. (1) Sulphide Sˉˉ :-- Parent Acid:- H2S (weak acid)H2S ↔ H* + HS ˉ ( hydro sulphide)HS ˉ↔ H*+ Sˉ(Sulphide )

  8. Dry Test :- (Actions of Dil.Hcl )-Sˉˉ + 2H*→H2S gas ↑↑or Na2S + 2HCl → H2S ↑↑ + 2 NaClH2S 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

  9. Pb(Ac)2 + H2S → PbS ↓↓ Black pptPb** + H2S →PbS ↓↓Black pptWet Reactions : -- Reactions with BaCl2:- ( - ve )-Reactions with AgNO3(Silvernitrate):Sˉˉ + 2Ag* → Ag2S ↓↓ Black pptwhich is soluble in Dil.HNO3 , Insoluble in Ammonia and KcN

  10. -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)

  11. (2) Sulphite SO3ˉˉ :- - Parent Acid :- H2SO3 Sulphurous Acidweak 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 )

  12. Note : Sulphite Has Reducing properties Cr2O7ˉˉ + 2 H* + SO2 → SO4ˉˉ + 2Cr*** (green colour )+ H2O

  13. (-)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 )

  14. 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 )

  15. -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 )

  16. -Reaction with FeCl3 :-2Fe** + 3SO3ˉˉ → Fe(SO3)2 (Red complex) Fe(SO3)2(Δ)→Reddish Brown ppt of Basic iron salt

  17. 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)

  18. 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 Godwilling,the second half will be soon PH Mohamed Hamdy

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