Page 67 - Chemistry - XI

Colourless solution (Pb ) Bluish green solution (Cu )
+2
+2
Add dilute H SO and little ethanol. A white ppt. Boil off H S and divide the solution into two
4
2
2
is formed. parts:
Dissolve the white ppt. in ammonium acetate
solution and divide into two parts:
(i) Potassium iodine (KI) test: To the fi rst (i) Ammonium hydroxide (NH OH) test:
4
part, add KI solution → Yellow ppt. To one part, add NH OH solution in excess
4
(ii) Potassium chromate (K CrO ) test: To with shaking → Deep blue solution.
2 4

the second part, add K CrO solution → (ii) Potassium ferrocyanide KFeCN
4
6
4
2
Yellow ppt. soluble in NaOH solution. test: Acidify second part with little acetic

acid and add KFeCN solution →
6
4
Chocolate brown ppt.
Pb Confi rmed Cu Confi rmed
+2
+2
Chemical Reactions
Test for Pb +2
Pb +H S PbS +2H +
+2
2
B lack ppt.

PbS+ 2HNO Pb NO +H S
3 3 2 2
Black pppt.

Pb NO +H SO PbSO +2HNO
3 2 2 4 4 3
Whiite ppt.
1. KI test:

Pb CH COO+ 2KI PbI +2CH COOK
3
2
3
2
Yellow ppt.

2. K CrO test:
2 4

Pb CH COO+ KCrO PbCrO + 2CHCOOK
3
4
4
2
3
2
Yellow ppt.

PbCrO+ 2NaOH NaCrO +PbOH
4 2 4 2
Soluble

Test for Cu +2
Cu +H S CuS +2H +
+2
2
Black ppt.

3CuS+8HNO 3CuNO + 2NO+ 4H O+3S
3 3 2 2
1. NH OH test:
4
Cu NO +2NH OH Cu OH +2NH NO

Blue ppt.
3 2 4 2 4 3

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