2. By PH Mohamed Hamdy

3. Analytical chemistry second part of lecture (2) lecturer : Dr.Magda

4. In this lecture we take about : (3)ThioSulphate (S 2 O 3 ˉˉ):- -Parent acid :- H 2 S 2 O 3 Thiosulphuric acid -DryTest :- S 2 O 3 ˉˉ + 2H* → H 2 S 2 O 3 ↓∆ H2O+SO2↑+S˚↓ Thiosulphuric acid easily decomposed to give colloidal sulphur with yellow colour thiosulphuric acid has Reducing Properties

5. -Wet Reactions :-.Reaction with BaCl 2 :- It gives No ppt in Dil.solution But ppt is formed in conc.solution Ba** + conc.S 2 O 3 → BaS 2 O 3 ↓ ↓Boil BaSO 4 ↓ ( white ppt )

6. .Reaction with AgNO 3 :- 2Ag* + S 2 O 3 ˉˉ → Ag 2 S 2 O 3 ↓White ppt ↓H 2 O H 2 SO 4 + Ag 2 S↓↓ (Black ppt) It gives white ppt of (Ag 2 S 2 O 3) silver thio sulphate which changes its colour on standing from white → yellow →Brown → Black

7. .Reaction with Pb(Ac) 2 :- Pb** + S 2 O 3 ˉˉ→PbS 2 O 3 ↓ ↓Boil PbS ↓↓ (Black ppt.It gives white ppt of lead thiosulphate (PbS 2 O 3 ) which is soluble in cold.HNO 3.On Boiling give black ppt of (PbS)

8. .Reaction with FeCl 3 :- Fe*** + 2S 2 O 3 ˉˉ → [Fe(S 2 O 3 ) 2 ]ˉ ( purple complex) ↓∆ 2Fe** + S 4 O 6 ˉˉ.It gives purple colour of [Fe(S 2 O 3 ) 2 ]ˉcomplex ferric thiosulphate.on Boiling purple colour Disappear and formation of Fe** and tetrathionate S 4 O 6ˉˉ

9. Q:prove that Sˉˉ,SO 3 ˉˉ,S 2 O 3 ˉˉHave Reducing properties ??? A-Reaction with I2(iodine):- Sˉˉ SO 3 ˉˉ S 2 O 3 ˉˉ ↓I 2 /H* ↓I 2 /H* ↓I 2 /H* 2Iˉ+S˚ 2Iˉ+SO 4 ˉˉ S˚+2Iˉ+S 4 O 6 ˉˉ By addition of I 2 in acidic media (Brown solution ) to Sˉˉ,SO 3 ˉˉ,S 2 O 3ˉˉ leads to discolouration of brown colour of I 2 solution and give colours solution

10. You also can prove that by B-Reaction with K 2 Cr 2 O 7 :- C-Reaction with KMnO4 (pot.permenganate) Dr.Magda said that you can use A or B or C to prove that but you should also know B and C so depend on your self to get them

11. (4)Sulphate SO4ˉˉ :- -Parent Acid: H2SO4 Sulphuric Acid -Dry Test:- SO4ˉˉ + 2H* → -ve ( means no rection)

12. Important notes :.General properties of Sulphuric Acid 1- one of the strongest acids 2-Ionizes in dilute solution in 2 steps H 2 SO 4 ↔ H* + H 2 SO 4 ˉ H 2 SO 4 ˉ↔ H* + SO 4 ˉˉ 3-It has Dehydrating properties :- concerated H 2 SO 4 has great tendency ( ميل او قابلية ) to combine with water to form stable Hydrates ( H 2 SO 4.H 2 O)

13. H 2 SO 4 ALSO : can extract H 2 O from certain substances C 2 H 5 -OH + H 2 SO 4 →C 2 H 4 + H 2 SO 4.H 2 O (Hydrated sulphuric a) and cause charring to sugars due to removing water from them

14. 4-H 2 SO 4 Has Oxidising properties : It is moderately oxidising agent when heated with most reducing agents H 2 SO 4 (▲)→H 2 O + SO 2 +[O] H 2 SO 4 +8HI→H 2 S + 4I 2 +4H 2 O SOOOOOO NEVER SAY Sulphuric acid act as reducing agent it is oxidising agent (ok?????)

15. -Wet Reactions:-.Reaction with BaCl 2 : Ba** + SO 4 ˉˉ→ BaSO 4 ↓(white ppt) Note that BaSO 4 is insoluble in dil.HCl even upon boiling.Reaction with AgNO 3 : 2Ag* + SO 4 ˉˉ(conc.)→Ag 2 SO 4 ↓ (white ppt)

16. .Reactions with Pb(Ac) 2 : Pb** + SO 4 ˉˉ→ PbSO 4 ↓↓white ppt PbSO 4 + 3OHˉ→HPbO 2 ˉ+H 2 O +SO 4 ˉˉ Note that PbSO 4 ( lead sulphate) is insoluble in cold.dil.mineral acids but sol.in KI ana Ammonium Acetate solution

17. .Reaction with FeCl 3 : (-ve) No reaction that was about SO 4 ˉˉ Let’s see what next

18. (5)PerSulphate S 2 O 8 ˉˉ: All Reactions of S 2 O 8 ˉˉon cold is – ve (negative) No reaction occur.Dry Test: S 2 O 8 ˉˉ + H 2 O (▲)→SO 4 ˉˉ + H 2 SO 4 +[O] ↓HCl ↑ Cl 2

19. -Wet Reactions:.Reaction of BaCl 2 : S 2 O 8 ˉˉ+H 2 O(▲)→SO 4 ˉˉ ↓Ba** BaSO 4 ↓white ppt.Reactions with AgNO 3 : S 2 O 8 ˉˉ+2H 2 O+2Ag*(▲)→Ag 2 O 2 ↓ +2H 2 SO 4 (black ppt)

20. .Reaction with Pb(Ac) 2 : No reaction on cold, on boiling Brown pt of Hydrated peroxide appear.Reaction with FeCl 3 : NO REACTION

21. SPECIAL TEST : ( SO IMPORTANT) 1-For Sˉˉ: a-Cadmium carbonateTest: Cd** + Sˉˉ→CdS ↓yellow ppt sulphide solution is shaken with CdCO 3 →yellow ppt of CdS produced b-Sodium Nitro Prusside Test: Sˉˉ+[Fe(CN) 5 NO]ˉˉ→ [Fe(CN) 5 NOS]ˉˉˉˉ (purple colour)

22. 2-for Sulphite SO 3 ˉˉ: Zinc Nitro prusside Test: ZnSO 4 +K 4 [Fe(CN) 6 ]+ Sod.nitro prusside + SO 3 ˉˉ→Red colour of Zn[Fe(CN) 5 NO]+ moist SO 2 → Na 5 [Fe(CN) 5 SO 3 ] (red complex)

23. 3-For ThioSulphate S 2 O 3 ˉˉ: Thiocyanate test: S 2 O 3 ˉˉ+CNˉ(boiling alkaline) → SCNˉ+SO 3 ˉˉ H* ↓Fe*** Fe(SCN) 3 or [Fe(SCN)]** (red blood colour)

24. 4-For sulphate SO 4 ˉˉ: Hepar’s Test: MSO 4 + Na 2 CO 3 (fusion)→Na 2 SO 4 + MCO 3 ↓carbon Na 2 S+4CO↑ ↓H 2 O Ag 2 S ←Ag*+H 2 S (black ppt) SO 4 ˉˉis reduced by (C) to Sˉˉ by heating on piece of charcoal in prescence of Na 2 CO 3

25. 5-For persulphate S 2 O 8 ˉˉ: Depend on their oxidising properties 1- S 2 O 8 ˉˉ+ 2Iˉ→I 2 (brow) + SO 4 ˉˉ ↓starch blue 2- 5S 2 O 8 ˉˉ+2Mn**(manganous)+ 8H*→2MnO 4 + 10SO 4 ˉˉ+6H* (pink colour)

26. Analysis of mixtures of Sˉˉ,SO 3 ˉˉ, S 2 O 3 ˉˉ,SO 4 ˉˉ

27. Sˉˉ, SO 2 ˉˉ, S 2 O 3 ˉˉ, SO 4 ˉˉ Centrifugate + BaCl2 White ppt BaSO4 + BaSO3+Dil.Hcl White ppt BaSO4 SO4ˉˉ Centrifugate SO3ˉˉ Cnfirmed by oxidation with Br2 or H2O into SO4ˉˉ Centrifugate BaS2O3 + Dil.HCl ↓▲ ↑SO2=S CdS Yellow ppt

28. YOU should look on these pages in the book 21, 22,23

29. المصادر الكتاب – ورق الشروق الحمدلله الذى هدانا الى هذا و ما كنا لنهتدى لولا أن هدانا الله و ان قدر الله لك ان تستفيد بهذا و لو معلومة واحدة فاسالك بها دعوة بظهر الغيب و أخــــــــــــــــــــــيــــرا