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Qualitative Analysis
Istvan Szalai
Institute of Chemistry, Eotvos University
2016
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
The cations of Group I can be precipitated as sulfides from acidicsolution (pH∼2) by H2S; the precipitates are insoluble in (NH4)2Sand KOH.
The cations of Group II can be precipitated in acidic media withH2S but the sulfides of are soluble in (NH4)2Sx and KOH withformation of thiocomplexes.
The cations of Group III can be precipitated with (NH4)2S inneutral or slightly alkaline solutions, but cannot be precipitatedwith H2S in acidic solutions.
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
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, Hg2Cl2, PbCl2
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
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, Hg2Cl2, PbCl2
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
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 ,Zn(OH)2−4 , Al(OH)−4
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
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)2Soluble in excess of NaOH:Pb(OH)2−4 , Sn(OH)2−4 , Sn(OH)2−6 , Sb(OH)−4 , Sb(OH)−6 ,Zn(OH)2−4 , Al(OH)−4
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
NaOH (2M):Colored precipitates:Ag2O, 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 H2O2 in basic solution:Ag2O, HgOCan be oxidized by H2O2 in basic solution:Co(OH)2, Cr(OH)3, Mn(OH)2, Fe(OH)2
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
NaOH (2M):Colored precipitates:Ag2O, HgO, Cu(OH)2, Ni(OH)2, Co(OH)2, Mn(OH)2, Fe(OH)2,Fe(OH)3, Cr(OH)3Soluble in excess:Cr(OH)−4
Can be reduced by H2O2 in basic solution:Ag2O, HgOCan be oxidized by H2O2 in basic solution:Co(OH)2, Cr(OH)3, Mn(OH)2, Fe(OH)2
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
NaOH (2M):Colored precipitates:Ag2O, HgO, Cu(OH)2, Ni(OH)2, Co(OH)2, Mn(OH)2, Fe(OH)2,Fe(OH)3, Cr(OH)3Soluble in excess:Cr(OH)−4
Can be reduced by H2O2 in basic solution:Ag2O, HgOCan be oxidized by H2O2 in basic solution:Co(OH)2, Cr(OH)3, Mn(OH)2, Fe(OH)2
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
NH3 (2M):The first reaction is the same like with NaOH (except Hg(I) andHg(II)).
Complex formation in excess of NH3:Ag(NH3)+2 , Cd(NH3)2+4 , Zn(NH3)2+4 , Cu(NH3)2+4 , Ni(NH3)2+6 ,Co(NH3)2+6
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
NH3 (2M):The first reaction is the same like with NaOH (except Hg(I) andHg(II)).Complex formation in excess of NH3:Ag(NH3)+2 , Cd(NH3)2+4 , Zn(NH3)2+4 , Cu(NH3)2+4 , Ni(NH3)2+6 ,Co(NH3)2+6
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
H2S (pH=2):Black or brown precipitates:Bi2S3, PbS, HgS, CuS, Ag2S, SnS
Yellow or orange precipitates:Sb2S3, CdS, SnS2, As2S3
White precipitates (in buffered or basic solution): ZnSRedox reaction: Fe3+, As(V), Sb(V)
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
H2S (pH=2):Black or brown precipitates:Bi2S3, PbS, HgS, CuS, Ag2S, SnSYellow or orange precipitates:Sb2S3, CdS, SnS2, As2S3
White precipitates (in buffered or basic solution): ZnSRedox reaction: Fe3+, As(V), Sb(V)
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
H2S (pH=2):Black or brown precipitates:Bi2S3, PbS, HgS, CuS, Ag2S, SnSYellow or orange precipitates:Sb2S3, CdS, SnS2, As2S3
White precipitates (in buffered or basic solution): ZnSRedox reaction: Fe3+, As(V), Sb(V)
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
(NH4)2S:Black or brown precipitates:Bi2S3, PbS, HgS, CuS, Ag2S, NiS, CoS, FeS, Fe(OH)3
Other precipitates:ZnS, CdS, MnS, Cr(OH)3, Al(OH)3Thiocomplexes:AsS3−
3 , AsS3−4 , SbS3−
3 , SbS3−4 , SnS3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
(NH4)2S:Black or brown precipitates:Bi2S3, PbS, HgS, CuS, Ag2S, NiS, CoS, FeS, Fe(OH)3Other precipitates:ZnS, CdS, MnS, Cr(OH)3, Al(OH)3
Thiocomplexes:AsS3−
3 , AsS3−4 , SbS3−
3 , SbS3−4 , SnS3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
(NH4)2S:Black or brown precipitates:Bi2S3, PbS, HgS, CuS, Ag2S, NiS, CoS, FeS, Fe(OH)3Other precipitates:ZnS, CdS, MnS, Cr(OH)3, Al(OH)3Thiocomplexes:AsS3−
3 , AsS3−4 , SbS3−
3 , SbS3−4 , SnS3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KI:Colored precipitates:BiI3, Hg2I2, HgI2, PbI2, AgI, CuI
Complexes:BiI−4 , HgI2−4 , CdI2−4 , (PbI2−4 ), (AgI−2 ), (CuI−2 )Redox reaction:Cu2+, Fe3+, As(V), Sb(V)
I2 (I−3 ):In acidic solution: Sn(II)After adding NaHCO3: AsO3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KI:Colored precipitates:BiI3, Hg2I2, HgI2, PbI2, AgI, CuIComplexes:BiI−4 , HgI2−4 , CdI2−4 , (PbI2−4 ), (AgI−2 ), (CuI−2 )
Redox reaction:Cu2+, Fe3+, As(V), Sb(V)
I2 (I−3 ):In acidic solution: Sn(II)After adding NaHCO3: AsO3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KI:Colored precipitates:BiI3, Hg2I2, HgI2, PbI2, AgI, CuIComplexes:BiI−4 , HgI2−4 , CdI2−4 , (PbI2−4 ), (AgI−2 ), (CuI−2 )
Redox reaction:Cu2+, Fe3+, As(V), Sb(V)
I2 (I−3 ):In acidic solution: Sn(II)After adding NaHCO3: AsO3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KI:Colored precipitates:BiI3, Hg2I2, HgI2, PbI2, AgI, CuIComplexes:BiI−4 , HgI2−4 , CdI2−4 , (PbI2−4 ), (AgI−2 ), (CuI−2 )Redox reaction:Cu2+, Fe3+, As(V), Sb(V)
I2 (I−3 ):In acidic solution: Sn(II)After adding NaHCO3: AsO3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KI:Colored precipitates:BiI3, Hg2I2, HgI2, PbI2, AgI, CuIComplexes:BiI−4 , HgI2−4 , CdI2−4 , (PbI2−4 ), (AgI−2 ), (CuI−2 )Redox reaction:Cu2+, Fe3+, As(V), Sb(V)
I2 (I−3 ):In acidic solution: Sn(II)After adding NaHCO3: AsO3−
3
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KMnO4 (slightly acidic solution):Sn(II), Fe(II), Hg2+2 , Sb(III), As(III)
Zn:Acidic solution:Ag+, Cu2+, Hg2+2 , Hg2+, Bi3+, As(III), As(V), Sb(III), Sb(V),Sn(II), Sn(IV), (Cd2+), (Pb2+), (Ni2+), (Co2+)Fe(III)−→ Fe(II)
Istvan Szalai Qualitative Analysis
Cations (Group I-III)
KMnO4 (slightly acidic solution):Sn(II), Fe(II), Hg2+2 , Sb(III), As(III)
Zn:Acidic solution:Ag+, Cu2+, Hg2+2 , Hg2+, Bi3+, As(III), As(V), Sb(III), Sb(V),Sn(II), Sn(IV), (Cd2+), (Pb2+), (Ni2+), (Co2+)Fe(III)−→ Fe(II)
Istvan Szalai Qualitative Analysis
Midterm 1
Date: March 17th 2016, 12:15-13:45Tools: pen, calculator (non programmable)The use of mobilephone (iphone) is forbidden!
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
Does the ZnS precipitate form in a solution which is 0.1M foraceteic acid and 0.01M for Zn2+ ions and saturated with H2S?
Ka(CH3COOH) = 2× 10−5, Ka1(H2S) = 1× 10−7
Ka2(H2S) = 1× 10−13, Ksp = 1× 10−21
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
[H+] =√
[CH3COOH]Ka =√
0.1× 2× 10−5 = 1.41× 10−3M
αH =
(1 +
1.41× 10−3
10−13+
(1.41× 10−3)2
10−1310−7
)= 1.98× 1014
[S2−] =[S2−]tαH
=0.1
1.98× 1014= 5× 10−16
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
[H+] =√
[CH3COOH]Ka =√
0.1× 2× 10−5 = 1.41× 10−3M
αH =
(1 +
1.41× 10−3
10−13+
(1.41× 10−3)2
10−1310−7
)= 1.98× 1014
[S2−] =[S2−]tαH
=0.1
1.98× 1014= 5× 10−16
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
[H+] =√
[CH3COOH]Ka =√
0.1× 2× 10−5 = 1.41× 10−3M
αH =
(1 +
1.41× 10−3
10−13+
(1.41× 10−3)2
10−1310−7
)= 1.98× 1014
[S2−] =[S2−]tαH
=0.1
1.98× 1014= 5× 10−16
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
[S2−] =[S2−]tαH
=0.1
1.98× 1014= 5× 10−16
Q = [Zn2+][S2−] = 10−2 × 5× 10−16 = 5× 10−18
Q = 5× 10−18 > Ksp = 1× 10−21
The precipitation of ZnS occurs at this conditions.
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
[S2−] =[S2−]tαH
=0.1
1.98× 1014= 5× 10−16
Q = [Zn2+][S2−] = 10−2 × 5× 10−16 = 5× 10−18
Q = 5× 10−18 > Ksp = 1× 10−21
The precipitation of ZnS occurs at this conditions.
Istvan Szalai Qualitative Analysis
Solubility of sulfides in acidic solutions
Zn2+ + S2− −−⇀↽−− ZnSS2− + H+ −−⇀↽−− HS−
HS− + H+ −−⇀↽−− H2S
[S2−] =[S2−]tαH
=0.1
1.98× 1014= 5× 10−16
Q = [Zn2+][S2−] = 10−2 × 5× 10−16 = 5× 10−18
Q = 5× 10−18 > Ksp = 1× 10−21
The precipitation of ZnS occurs at this conditions.
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3
I−
Cr3+
Cu2+
Hg2+
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3
I−
Cr3+
Cu2+
Hg2+
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I−
Cr3+
Cu2+
Hg2+
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+
Cu2+
Hg2+
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+
Hg2+
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+ +
SnCl2−4Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+ +
SnCl2−4 +
Ag+
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+ +
SnCl2−4 +
Ag+ +
Cd2+
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+ +
SnCl2−4 +
Ag+ +
Cd2+ +
SbCl−4Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following ions give precipitate with ammonium-sulfidein neutral solution?
Yes No
AsO3−3 +
I− +
Cr3+ +
Cu2+ +
Hg2+ +
Yes No
Al3+ +
SnCl2−4 +
Ag+ +
Cd2+ +
SbCl−4 +Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2Al(OH)3
Cr2(SO4)3PbSO4
Ni(OH)2
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3Cr2(SO4)3
PbSO4
Ni(OH)2
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3PbSO4
Ni(OH)2
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4
Ni(OH)2
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4
Ni(OH)2
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS +
As2O3
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS +
As2O3 +
Sb2S3
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS +
As2O3 +
Sb2S3 +
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS +
As2O3 +
Sb2S3 +
ZnSO4
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS +
As2O3 +
Sb2S3 +
ZnSO4 +
AgClWrite the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the following can not be dissolved in water, but can bedissolved in sodium-hidroxide?
Yes No
Cd(OH)2 +
Al(OH)3 +
Cr2(SO4)3 +
PbSO4 +
Ni(OH)2 +
Yes No
PbS +
As2O3 +
Sb2S3 +
ZnSO4 +
AgCl +Write the reactions:
Istvan Szalai Qualitative Analysis
Midterm 1
What single reagent could be used to distinguish between membersof the following pairs?
I CdS, SnS2
I Pb(OH)2−4 , Sn(OH)2−4I Sn(Cl)2−4 , Sb(Cl)−4I Cu(NH3)2+4 , Ni(NH3)2+6
Istvan Szalai Qualitative Analysis
Midterm 1
What single reagent could be used to distinguish between membersof the following pairs?
I CdS, SnS2
NaOH
I Pb(OH)2−4 , Sn(OH)2−4I Sn(Cl)2−4 , Sb(Cl)−4I Cu(NH3)2+4 , Ni(NH3)2+6
Istvan Szalai Qualitative Analysis
Midterm 1
What single reagent could be used to distinguish between membersof the following pairs?
I CdS, SnS2
NaOH
I Pb(OH)2−4 , Sn(OH)2−4Bi(OH)3
I Sn(Cl)2−4 , Sb(Cl)−4I Cu(NH3)2+4 , Ni(NH3)2+6
Istvan Szalai Qualitative Analysis
Midterm 1
What single reagent could be used to distinguish between membersof the following pairs?
I CdS, SnS2
NaOH
I Pb(OH)2−4 , Sn(OH)2−4Bi(OH)3
I Sn(Cl)2−4 , Sb(Cl)−4Hg2+
I Cu(NH3)2+4 , Ni(NH3)2+6
Istvan Szalai Qualitative Analysis
Midterm 1
What single reagent could be used to distinguish between membersof the following pairs?
I CdS, SnS2
NaOH
I Pb(OH)2−4 , Sn(OH)2−4Bi(OH)3
I Sn(Cl)2−4 , Sb(Cl)−4Hg2+
I Cu(NH3)2+4 , Ni(NH3)2+6Fe
Istvan Szalai Qualitative Analysis
Midterm 1
How can you identify
I Cd2+ Cu2+ in presence of
I Zn2+ Pb2+ in presence of
I Ca2+ Ba2+ in presence of
Istvan Szalai Qualitative Analysis
Midterm 1
How can you identify
I Cd2+ Cu2+ in presence ofNH3, KCN,H2S
I Zn2+ Pb2+ in presence of
I Ca2+ Ba2+ in presence of
Istvan Szalai Qualitative Analysis
Midterm 1
How can you identify
I Cd2+ Cu2+ in presence ofNH3, KCN,H2S
I Zn2+ Pb2+ in presence ofNH3, (NH4)2S
I Ca2+ Ba2+ in presence of
Istvan Szalai Qualitative Analysis
Midterm 1
How can you identify
I Cd2+ Cu2+ in presence ofNH3, KCN,H2S
I Zn2+ Pb2+ in presence ofNH3, (NH4)2S
I Ca2+ Ba2+ in presence of(NH4)2(COO)2
Istvan Szalai Qualitative Analysis
Midterm 1
How can you identify Co(II), Cu(II) and Fe(III) ions in presence ofeach other?
Istvan Szalai Qualitative Analysis
Midterm 1
How can you identify Co(II), Cu(II) and Fe(III) ions in presence ofeach other?
I Fe
I NH4SCN, NaF
Istvan Szalai Qualitative Analysis
Midterm 1
Which of the substance can be identified by following the nextdescription?
1. White crystalline compound, that dissolves in water. Thesolution is colorless and acidic.
2. White precipitate forms with ammonia, which can not bedissolved in excess of ammonia.
3. White precipitate forms with sodium-hidroxide, which can bedissolved in excess of sodium-hidroxide. Boiling the alkalinesolution no change and no specific odour can be obderved.
4. White precipitate forms with perchloric acid from the originalsolution.
5. White precipitate forms with barium-chloride, which can notbe dissolved in 20% HCl.
Istvan Szalai Qualitative Analysis
Midterm 1
1. White crystalline compound, that dissolves in water. Thesolution is colorless and acidic.Excluded ions: Cu(II), Co(II), Ni(II), Cr(III), Fe(II), Fe(III),Mn(II)
2. White precipitate forms with ammonia, which can not bedissolved in excess of ammonia.One of these ions must be: Hg(I), Hg(II), Pb(II), Bi(III),Sn(II), Sn(IV), Al(III), Mg2+
No informations about: Ag+, Cd2+, As(III), As(V), Ca2+,Ba2+, Na+, K+, NH +
4
Istvan Szalai Qualitative Analysis
Midterm 1
1. White crystalline compound, that dissolves in water. Thesolution is colorless and acidic.Excluded ions: Cu(II), Co(II), Ni(II), Cr(III), Fe(II), Fe(III),Mn(II)
2. White precipitate forms with ammonia, which can not bedissolved in excess of ammonia.One of these ions must be: Hg(I), Hg(II), Pb(II), Bi(III),Sn(II), Sn(IV), Al(III), Mg2+
No informations about: Ag+, Cd2+, As(III), As(V), Ca2+,Ba2+, Na+, K+, NH +
4
Istvan Szalai Qualitative Analysis
Midterm 1
3. White precipitate forms with sodium-hidroxide, which can bedissolved in excess of sodium-hidroxide. Boiling the alkalinesolution no change and no specific odour can be obderved.Excluded ions: Ag+, Cd2+, Hg(I), Hg(II), Bi(III),Mg2+, NH +
4
Possible ions: Pb2+ vagy Al3+
No infos: As(III), As(V), Ca2+, Ba2+, Na+, K+
Istvan Szalai Qualitative Analysis
Midterm 1
4. White precipitate forms with perchloric acid from the originalsolution.K+
5. White precipitate forms with barium-chloride, which can notbe dissolved in 20% HCl.SO 2–
4 !, excluded ions Pb2+, Ca2+, Ba2+
Possible ion Al3+, and no infos about As(III), As(V), Na+.
Substance:KAl(SO4)2
Istvan Szalai Qualitative Analysis
Midterm 1
4. White precipitate forms with perchloric acid from the originalsolution.K+
5. White precipitate forms with barium-chloride, which can notbe dissolved in 20% HCl.SO 2–
4 !, excluded ions Pb2+, Ca2+, Ba2+
Possible ion Al3+, and no infos about As(III), As(V), Na+.
Substance:KAl(SO4)2
Istvan Szalai Qualitative Analysis
Midterm 1
How many iron(II)-chloride can be dissolved in a mixture of 50cm3 0.1 mol/dm3 acetic acid and 50 cm3 0.1 mol/dm3
sodium-hidroxide?MM(iron(II)-chloride)=127 g/mol, Ksp = 1× 10−14
Ks(acetic acid) = 2× 10−5
Istvan Szalai Qualitative Analysis
Midterm 1
How many gramms of sodium-hydroxide (MM=40) is dissolved in100 cm3 of 0.25 mol/dm3 acetic acid if the pH is 5.0? What is thesolubility of the ZnS in this solution after saturating with H2S(cH2S = 0.1 mol/dm3)?Ksp = 1× 10−21
Ka(acetic acid)= 2× 10−5
Ka1(H2S)= 10−7
Ka2(H2S)= 10−13
Istvan Szalai Qualitative Analysis