Qualitative Analysis. István Szalai. Institute of Chemistry, Eötvös University

Transcription

1 Institute of Chemistry, Eötvös University 2011

2 Solubility of sulfides in acidic solutions Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S Does the ZnS precipitate form in a solution which is 0.1M for aceteic acid and 0.01M for Zn 2+ ions and saturated with H 2 S? K a (CH 3 COOH) = , K a1 (H 2 S) = K a2 (H 2 S) = , K sp =

3 Solubility of sulfides in acidic solutions Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S [H + ] = [CH 3 COOH]K a = = M

4 Solubility of sulfides in acidic solutions Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S [H + ] = [CH 3 COOH]K a = = M α H = ( ( ) 2 ) =

5 Solubility of sulfides in acidic solutions Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S [H + ] = [CH 3 COOH]K a = = M α H = ( ( ) 2 ) = [S 2 ] = [S 2 ] t α H = 0.1 =

6 Solubility of sulfides in acidic solutions [S 2 ] = [S 2 ] t α H = Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S 0.1 =

7 Solubility of sulfides in acidic solutions [S 2 ] = [S 2 ] t α H = Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S 0.1 = Q = [Zn 2+ ][S 2 ] = =

8 Solubility of sulfides in acidic solutions [S 2 ] = [S 2 ] t α H = Zn 2+ + S 2 ZnS S 2 + H + HS HS + H + H 2 S 0.1 = Q = [Zn 2+ ][S 2 ] = = Q = > K sp = The precipitation of ZnS occurs at this conditions.

9 The cations of Group I can be precipitated as sulfides from acidic solution (ph 2) by H 2 S; the precipitates are insoluble in (NH 4 ) 2 S and KOH. The cations of Group II can be precipitated in acidic media with H 2 S but the sulfides of are soluble in (NH 4 ) 2 S x and KOH with formation of thiocomplexes. The cations of Group III can be precipitated with (NH 4 ) 2 S in neutral or slightly alkaline solutions, but cannot be precipitated with H 2 S in acidic solutions.

10 Hydrolysis (ph=5): Bi(OH) 3, Sb(OH) 3, SbO(OH) 3, Sn(OH) 2, Sn(OH) 4, Al(OH) 3, Cr(OH) 3, Fe(OH) 3

11 Hydrolysis (ph=5): Bi(OH) 3, Sb(OH) 3, SbO(OH) 3, Sn(OH) 2, Sn(OH) 4, Al(OH) 3, Cr(OH) 3, Fe(OH) 3 HCl: AgCl, Hg 2 Cl 2, PbCl 2

12 NaOH (2M): White precipitates: Bi(OH) 3, Pb(OH) 2, Cd(OH) 2, Sn(OH) 2, Sn(OH) 4, Sb(OH) 3, SbO(OH) 3, Al(OH) 3, Zn(OH) 2

13 NaOH (2M): White precipitates: Bi(OH) 3, Pb(OH) 2, Cd(OH) 2, Sn(OH) 2, Sn(OH) 4, Sb(OH) 3, SbO(OH) 3, Al(OH) 3, Zn(OH) 2 Soluble in excess of NaOH: Pb(OH) 2 4, Sn(OH)2 4, Sn(OH)2 6, Sb(OH) 4, Sb(OH) 6 (!KOH), Zn(OH) 2 4, Al(OH) 4

14 NaOH (2M): Colored precipitates: Ag 2 O, HgO, Cu(OH) 2, Ni(OH) 2, Co(OH) 2, Mn(OH) 2, Fe(OH) 2, Fe(OH) 3, Cr(OH) 3

15 NaOH (2M): Colored precipitates: Ag 2 O, HgO, Cu(OH) 2, Ni(OH) 2, Co(OH) 2, Mn(OH) 2, Fe(OH) 2, Fe(OH) 3, Cr(OH) 3 Soluble in excess: Cr(OH) 4

16 NaOH (2M): Colored precipitates: Ag 2 O, HgO, Cu(OH) 2, Ni(OH) 2, Co(OH) 2, Mn(OH) 2, Fe(OH) 2, Fe(OH) 3, Cr(OH) 3 Soluble in excess: Cr(OH) 4 Can be reduced by H 2 O 2 in basic solution: Ag 2 O, HgO Can be oxidized by H 2 O 2 in basic solution: Co(OH) 2, Cr(OH) 3, Mn(OH) 2, Fe(OH) 2

17 NH 3 (2M): The first reaction is the same like with NaOH (except Hg(I) and Hg(II)).

18 NH 3 (2M): The first reaction is the same like with NaOH (except Hg(I) and Hg(II)). Complex formation in excess of NH 3 : Ag(NH 3 ) + 2, Cd(NH 3) 2+ 4, Zn(NH 3) 2+ 4, Cu(NH 3) 2+ 4, Ni(NH 3) 2+ 6, Co(NH 3 ) 2+ 6

19 H 2 S (ph=2): Black or brown precipitates: Bi 2 S 3, PbS, HgS, CuS, Ag 2 S, SnS

20 H 2 S (ph=2): Black or brown precipitates: Bi 2 S 3, PbS, HgS, CuS, Ag 2 S, SnS Yellow or orange precipitates: Sb 2 S 3, CdS, SnS 2, As 2 S 3

21 H 2 S (ph=2): Black or brown precipitates: Bi 2 S 3, PbS, HgS, CuS, Ag 2 S, SnS Yellow or orange precipitates: Sb 2 S 3, CdS, SnS 2, As 2 S 3 White precipitates (in buffered or basic solution): ZnS Redox reaction: Fe 3+, As(V), Sb(V)

22 (NH 4 ) 2 S: Black or brown precipitates: Bi 2 S 3, PbS, HgS, CuS, Ag 2 S, NiS, CoS, FeS, Fe(OH) 3

23 (NH 4 ) 2 S: Black or brown precipitates: Bi 2 S 3, PbS, HgS, CuS, Ag 2 S, NiS, CoS, FeS, Fe(OH) 3 Other precipitates: ZnS, CdS, MnS, Cr(OH) 3, Al(OH) 3

24 (NH 4 ) 2 S: Black or brown precipitates: Bi 2 S 3, PbS, HgS, CuS, Ag 2 S, NiS, CoS, FeS, Fe(OH) 3 Other precipitates: ZnS, CdS, MnS, Cr(OH) 3, Al(OH) 3 Thiocomplexes: AsS 3 3, AsS3 4, SbS3 3, SbS3 4, SnS3 3

25 KI: Colored precipitates: BiI 3, Hg 2 I 2, HgI 2, PbI 2, AgI, CuI

26 KI: Colored precipitates: BiI 3, Hg 2 I 2, HgI 2, PbI 2, AgI, CuI Complexes: BiI 4, HgI2 4, CdI2 4, (PbI2 4 ), (AgI 2 ), (CuI 2 )

27 KI: Colored precipitates: BiI 3, Hg 2 I 2, HgI 2, PbI 2, AgI, CuI Complexes: BiI 4, HgI2 4, CdI2 4, (PbI2 4 ), (AgI 2 ), (CuI 2 )

28 KI: Colored precipitates: BiI 3, Hg 2 I 2, HgI 2, PbI 2, AgI, CuI Complexes: BiI 4, HgI2 4, CdI2 4, (PbI2 4 ), (AgI 2 ), (CuI 2 ) Redox reaction: Cu 2+, Fe 3+, As(V), Sb(V)

29 KI: Colored precipitates: BiI 3, Hg 2 I 2, HgI 2, PbI 2, AgI, CuI Complexes: BiI 4, HgI2 4, CdI2 4, (PbI2 4 ), (AgI 2 ), (CuI 2 ) Redox reaction: Cu 2+, Fe 3+, As(V), Sb(V) I 2 (I 3 ): In acidic solution: Sn(II) After adding NaHCO 3 : AsO 3 3

30 KMnO 4 (slightly acidic solution): Sn(II), Fe(II), Hg 2+ 2, Sb(III), As(III)

31 KMnO 4 (slightly acidic solution): Sn(II), Fe(II), Hg 2+ 2, Sb(III), As(III) Zn: Acidic solution: Ag +, Cu 2+, Hg 2+ 2, Hg2+, Bi 3+, As(III), As(V), Sb(III), Sb(V), Sn(II), Sn(IV), (Cd 2+ ), (Pb 2+ ), (Ni 2+ ), (Co 2+ ) Fe(III) Fe(II)