Page 52 - Chemistry - XI

S. No. Test Observation Inference
3. Flame test

Certain salts form (i) Persistent golden yellow Na indicated
+
volatile chlorides
with conc. HCl by
dipping the platinum
wire in conc. HCl and
touching it with given
salt, and heating it in

the fl ame of bunsen
burner and observe
the colour of fl ame.
(ii) Violet colour for short time K indicated
+
(iii) Apple green fl ame Ba indicated
+2
(iv) Crimson red fl ame Sr indicated
+2
(v) Brick red fl ame Ca indicated
+2
(vi) Immense blue surrounded by Cu indicated
+2
green fl ame

Paste of the mixture
in conc. HCl Platinum Wire

Fig. 7.1: Making a loop Fig. 7.2: Dipping the Platinum Wire Fig. 7.3: Introducing the
of Platinum Wire in the paste of Salt and HCl Wire to the Flame

PRELIMINARY AND CONFIRMATORY TESTS FOR ANIONS

The preliminary tests of anions are classifi ed into the following groups on the basis of their reaction with

sulphuric acid.

1. Dilute sulphuric acid group: Carbonate CO , sulphite SO , sulphide S 2 , nitrite NO , and
2

2
3

3

acetate CH COO anions are decomposed by dilute sulphuric acid. 2
3

2. Concentrated sulphuric acid group: Nitrate NO , chloride Cl , bromide Br , iodide ,

I

3
2
and oxalate CO are decomposed by concentrated sulphuric acid, but not by dilute sulphuric acid.
2
4

2
3. Special group: Sulphate SO is not aff ected by either dilute or concentrated sulphuric acid.
4
Note:
Note: The anions of dilute sulphuric acid group are also decomposed by concentrated sulphuric acid, The anions of dilute sulphuric acid group are also decomposed by concentrated sulphuric acid,
but only dilute sulphuric acid is used to test these anions.but only dilute sulphuric acid is used to test these anions.
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