Page 74 - Chemistry - XI

GROUP - V (Ba , Sr , Ca )
+2
+2
+2
Group V cations are precipitated as carbonates in presence of NH Cl and NH OH.
4
4
If all the four groups are absent, start with 5 mL of original solution. If fi ltrate of Group IV is used (in
case any group is present), boil it for some time to remove H S and to reduce the volume to one-third
2
of its original volume and cool. Now add a pinch of NH Cl, NH OH solution and saturated solution of
4
4
(NH ) CO . Warm the solution and allow it to stand for sometime. A white precipitate indicates the presence
3
4 2
of Group V. Retain the fi ltrate for the cations of Group VI.
The precipitate is dissolved in hot dilute acetic acid and test for Ba , Sr , and Ca strictly in the given
+2
+2
+2
order.
S. No. Ba +2 Sr +2 Ca +2
1. Potassium chromate Ammonium sulphate Ammonium oxalate
(K CrO) test: Add (NH ) SO test: To the (NH ) C O test: If Ba +2
4
2
2
4 2
4 2
4
4
K CrO solution to the fi rst second portion of the above and Sr are absent, add
+2
4
2
part → A yellow ppt. (If solution, add (NH ) SO 4 (NH ) C O solution to the
2
4 2
4
4 2
yellow ppt. is not obtained, solution → A white ppt. (If third part of the solution
perform the test for Sr ). white ppt. is not obtained, → A white ppt.
+2
perform the test for Ca ).
+2
2. Flame test: Perform the Flame test: The above ppt. Flame test: The above ppt.
fl ame test with the ppt. gives crimson red fl ame on gives brick red fl ame on
obtained above → Grassy performing fl ame test. performing fl ame test.
green fl ame.
Ba confi rmed Sr confi rmed Ca confi rmed
+2
+2
+2
Chemical Reactions
Test for Ba +2

Ba +NH CO BaCO +2NH +

2
4 2 3 3 4

W hite ppt.

BaCO +2CH COOH Ba COOCH + HO +CO
3 3 3 2 2 2
Potassium chromate test:

Ba COOCH + KCrO BaCrO +2CHCOOK
3 2 2 4 4 3
Yellow ppt.

Test for Sr +2

Sr +NH CO SrCO + 2NH +
+2
3
4 2 3 White ppt. 4

SrCO +2CH COOH + H+CO
Sr COOCH
3 3 3 2 2 2
Ammonium sulphate test:
Ammonium sulphate test:
Sr COOCH COOC
Sr COOC + NH SO SrSO +2CH COONH
3 2 4 2 4 4 3 4
White ppt.

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