Analysis of CationsII

Analysis of Cations Group Cations I Pb2+ II Pb2+ Cu2+

III IV

V

Cd2+ Fe2+,Fe3+ Al3+ Co2+  Ni2+ Mn2+ Zn2+ Ba2+ Sr 2+ Ca2+

VI

Mg2+

Reagent Dilute HCl H2S in the  presence of  Dilute HCl  NH4Cl(s) +  NH4OH H2S in the  presence of   NH4Cl(s) +  NH4OH

Precipitate PbCl2 PbS CuS CdS Fe(OH)3 Al (OH)3 CoS  NiS MnS ZnS (NH4)2CO3in the BaCO3, SrCO3, CaCO3  presence of   NH4Cl(s) +  NH4OH  NH4Cl (s) MgNH4PO4 + NH4OH +  Na2HPO4

Colour of Ppt White Black  Black  Yellow Reddish Brown Gelatinous white Black  Black  Buff(flesh) Dirty white White

White

Preparation of original solution(O.S) Take a small amount of the given salt in a test tube. Dissolve it in distilled water. If  it does not dissolve, heat it. If it is insoluble even after heating, dissolve the salt in minimum quantity of dilute HCl Experiment

Group 0

I denti denti fi cation  cation 

Salt + NaOH solution and heat

Confirmation 

Group 1

O S + NaOH +  Nessler’s reagent (K 2HgI4) O S + dilute HCl

Observation Inference  NH n cate Pungent smell of  4 Ammonia giving dense white fumes of NH4Cl with a glass rod dipped in concentrated HCl a sent  No smell of  4 Ammonia Brown precipitate of   NH4+confirmed  NH2HgO.HgI

White precipitate  No characteristic characteristic  precipitate Group II O S + dilute HCl and then pass Black precipitate H2S gas Yellow precipitate  No characteristic characteristic  precipitate Group III O S + NH4Cl(s) + excess Reddish brown ppt  NH4OH Gelatinous white

Pb2+ indicated Pb2+ absent Cu2+ indicated Cd2+ indicated Cu2+ and Cd2+ absent Fe3+ indicated Al3+ indicated

In case the salt is light green,Fe2+ may be  present.Then add 1 ml conc

 ppt  No characteristic  precipitate

Fe3+ & Al3+ absent

Group IV

Group V

Group VI

O S + NH4Cl(s)+ NH4OH and then pass H2S

O S + NH4Cl(s)+ NH4OH +conc. (NH4)2CO3(aq)

O .S + NH4Cl+ NH4OH +  Na2HPO4 solution

Black precipitate Flesh coloured  precipitate Dirty white  precipitate  No characteristic  precipitate White precipitate  No characteristic  precipitate Crystalline white  precipitate

Co2+ or Ni2+ indicated Mn2+ indicated Zn2+ indicated Co2+, Ni2+, Mn2+ and Zn2+ absent Ba2+ or Sr 2+ or Ca2+ indicated Ba2+ or Sr 2+ or Ca2+ absent Mg2+ identified and confirmed

Analysis of Group I

Group I

Boil the white precipitate in 5 ml of water and divide into two parts Part I +KI solution Part II + K 2CrO4 solution

Yellow precipitate Yellow precipitate

Pb2+ confirmed Pb2+ confirmed

Analysis of Group II Group II

Black precipitate + 50% HNO3 .Boil Confirmation of Cu 2+ Divide the blue solution into two parts

Part I + NH4OH

Part II

+ K 4[Fe(CN)6]

Confirmation of Cd 2+ Yellow precipitate + 3-4 ml of yellow ammonium sulphide .Warm .Divide into two parts Part I+ K 4[Fe(CN)6]

Part II + NH4OH

Precipitate dissolves to Pb2+ is give a colourless solution.  present.Confirma tion tests as given Precipitate dissolves above. to give a bluish green solution Cu2+ present A light blue precipitate Cu2+ confirmed dissolving in excess ammonia to give a deep  blue solution Chocolate brown  precipitate

Cu2+ confirmed

White or bluish white  precipitate

Cd2+ confirmed

White precipitate soluble in excess NH4OH

Cd2+ confirmed

Analysis of Group III Group III

Confirmation of Fe 3+ Dissolve the reddish brown  precipitate in dilute HCl and divide into two parts

Part I + K 4[Fe(CN)6] Part II + NH4CNS Confirmation of Al 3+ (Lake test) Dissolve the dirty white  precipitate in dilute HCl. Add two drops of blue litmus solution. Add NH4OH drop  by drop along the sides of the test tube

Prussian blue colouration Blood red colouration

Fe3+ confirmed

Blue precipitate floating in the colourless solution

Al3+ confirmed

Fe3+ confirmed

Analysis of Group IV Group IV

Confirmation of Zn 2+ Dissolve the dirty white  precipitate in dilute HCl. Boil off H2S. Divide the solution in two parts Part I + NaOH

Part II + K 4[Fe(CN)6]

Confirmation of Mn 2+ Dissolve the flesh coloured  precipitate in dilute HCl. Boil off H2S. Add NaOH Confirmation of Ni 2+ O S + NaOH O S + NH4OH + Dimethylglyoxime Confirmation of Co 2+ O.S+ NH4CNS + Acetone, shaken well

White precipitate which dissolves in excess NaOH White or bluish white  precipitate

Zn2+ confirmed

White precipitate which turns brown on standing

Mn2+ confirmed

Zn2+ confirmed

Apple green precipitate  Ni2+ confirmed Rosy red precipitate

Blue organic layer

 Ni2+ confirmed

Co2+ confirmed

Analysis of Group V

Group V

Dissolve the white precipitate in minimum quantity of acetic acid and divide the solution into three  parts.Test the three parts in the given sequence only. Part I + K 2CrO4

Yellow precipitate

Ba2+ confirmed

Make a paste of the white  precipitate with few drops of  concentrated HCl and introduce this into a flame using a glass rod Part II+ (NH4)2SO4

Apple green coloured flame

Ba2+ confirmed

White precipitate

Sr 2+ confirmed

Make a paste of the white  precipitate with few drops of  concentrated HCl and introduce

Crimson red coloured flame

Sr 2+ confirmed

SPECIMEN REPORT (Assuming the salt to be Al(NO3)3) SALT ANALYSIS

1

Experiment Note the colour of the salt

Observation White Crystalline

2

Note the odour of the salt

No characteristic smell

3

Solubility test To a pinch of salt taken in a test tube, add 2 ml of water  To a pinch of salt ad 2 ml of  dilute HCl Dry Heating test •

•

4

4

5

Flame test Take little salt in a watch glass. Add a drop or two of concentrated HCl and make a paste. Introduce the paste into a non luminous flame using a glass rod.

Salt + Dilute H2SO4

Soluble in water  Soluble in dilute HCl Droplets of water  near the mouth of  the test tube  No characteristic flame

Analysis of Anions  No gas evolved

6

Salt + Concentrated H2SO4

7

Confirmatory test for Nitrate (NO 3)-

Redish brown gas with pungent smell, gets intensified by addition of copper  turnings

Salt solution + freshly prepared FeSO4 A brown ring at the  junction of the two solution. Add concentrated H2SO4 solutions along the sides of the test tube

Inference Absence of Cu2+,  Ni2+, Mn2+, Co2+ and Fe3+  NH , CH COO an 4

3

S2- may be absent Absence of heavy metal carbonates Absence of Pb2+ Hydrated salt.

Absence of Ba2+, Sr 2+, Ca2+ and Cu2+

CO -, SO -, S 3

-

3

absent  NO - n cate 3

3

 NO

confirmed

ANALYSIS OF CATIONS

Group 0 Group I Group II Group III

IDENTIFICATION Experiment Observation Salt + NaOH  No smell of  solution and heat Ammonia O S + Dilute HCl No characteristic  precipitate O S + Dilute HCl  No characteristic  precipitate and pass H2S gas Gelatinous white OS + NH4Cl (s) +excess of NH4OH  precipitate

Inference a sent 4

Pb2+ absent Cu2+, Hg2+, Cd2- and AS3+ absent Al3+ indicated

ANALYSIS OF GROUP III Confirmation of Al 3+ (Lake Test)

Dissolve the dirty white  precipitate in dilute HCl. Add two drops of blue litmus solution. Add  NH4OH drop by drop along the sides of the test tube

Blue precipitate floating in the colourless solution

Al3+ confirmed

Result The given salt contains Nitrate (NO 3-) as the Anion and Aluminium (Al 3+) as the Cation.