Page 80 - Lab Manual & Project class 12

LABORATORY MANUAL CHEMISTRY
Chemistry of Confirmatory Tests of Group–V cations

The Group–V cations are precipitated as their carbonates which dissolve in acetic
acid due to the formation of corresponding acetates.
2+
1. Test for Barium ion (Ba )
(a) Potassium chromate (K CrO ) solution gives a yellow precipitate of barium
2
4
chromate when the solution of fifth group precipitate in acetic acid is treated
with it.
BaCO + 2CH COOH (CH COO) Ba + H O + CO
3 3 3 2 2 2
(CH COO) Ba + K CrO BaCrO + 2CH COOK
3 2 2 4 4 3
Barium chromate
(yellow precipitate )
(a)Maxbrain Chemistry
(b) Flame test : Take a platinum wire and dip it in conc. HCl. Heat it strongly
until the wire does not impart any colour to the non-luminous flame.
Now dip the wire in the paste of the (Group–V) precipitate in conc. HCl.
Heat it in the flame. A grassy green colour of the flame confirms the
presence of Ba ions.
2+
2+
2. Test for Strontium ion (Sr )
(a) Solution of V group precipitate in acetic acid gives a white precipitate of
strontium sulphate with ammonium sulphate, (NH ) SO , solution on
4
4 2
heating and scratching the sides of the test tube with a glass rod.
SrCO + 2CH COOH (CH COO) Sr + H O + CO
3 3 3 2 2 2
(CH COO) Sr + (NH ) SO SrSO + 2CH COONH
3 2 4 2 4 4 3 4
Strontium
sulphate
(White precipitate)
2+
(b) Flame test : Perform the flame test as given in the case of Ba . A crimson
2+
red flame confirms the presence of Sr ions.
2+
3. Test for Calcium ion (Ca )
Solution of the fifth group precipitate in acetic acid gives a white precipitate
with ammonium oxalate solution.
CaCO + 2CH COOH (CH COO) Ca + H O + CO 2
3
2
2
3
3
(CH COO) Ca + (NH ) C O (COO) Ca + 2CH COONH
3 2 4 2 2 4 2 3 4
Ammonium Calcium oxalate
oxalate (White precipitate)
(b) Flame test : Perform the flame test as mentioned above. Calcium imparts
brick red colour to the flame which looks greenish-yellow through blue glass.

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24-04-2018