14. To analyse the basic and acidic radicals of a given salt (CuSO4).

Aim:- To analyse the basic and acidic radicals of a given salt.

Physical appearance:-

Colour: Blue

Smell: Odourless

Appearance: Crystalline

Dry heating test:-

Procedure	Observation	Inference
Take a small amount of dry salt and heat it.	Salt becomes brown or black on heating.	Cu2+ is indicated.

Flame test:-

Procedure	Observation	Inference
Prepare a paste of the salt with concentrated HCL on a clean watch glass. Place small amount of this paste on platinum wire loop and introduce into the flame.	Bright bluish green flame.	Cu2+ may be present.

Test for independent radicals:-

Boil a small amount of salt with dilute HCL in a test tube. Filter the content and to the filtrate add few drops of BaCl₂ solution. A white precipitate, insoluble in concentrated HCl indicates presents of sulphate.

Confirmation of acid radicals by wet test:-

Aqueous solution or water extract:- shake a little of the salt with water. If the salt dissolves, this aqueous solution obtained is used for the wet tests of acid radicals and is called water extract (W.E).

Confirmation of sulphate (SO₄^2-):-

Procedure	Observation	Inference
(i) Barium chloride test :- To a part of the aqueous solution of salt add barium chloride solution.	A white precipitate is formed which is insoluble.	SO42- is present.
(ii) Lead acetate test:- To a part of aqueous solution of the salt add lead nitrate solution.	A white precipitate is formed which is soluble in excess ammonium acetate solution.	SO42-is present.

Preparation of solution for wet tests of basic radicals:-

If the salt is insoluble in distilled water, take a fresh quantity of salt in a clean test tube and try to first dissolve first in cold dilute HCL and then try to dissolve it in concentrated HCL. The clear5 solution thus obtained is labelled as original solution (O.S).

Analysis of group zero:-

Procedure	Observation	Inference
The solution is heated with concentrated NaOH.	No gas evolved.	Group zero is absent.

Analysis of group 1:-

Procedure	Observation	Inference
Original solution is prepared in water. Add dilute HCL to it.	No precipitate is formed.	Group 1 is absent.

Analysis of group 2:-

Procedure	Observation	Inference
Take about 2 ml of solution on a test tube. Add HCL and warm. Through this pass H2S gas.	Black precipitate is formed.	Group 2 is present.

Confirmation for Cu²⁺:- Heat the black precipitate with minimum quantity (1-2)ml of 50% HNO₃, precipitate dissolves. To one part of the above solution, add dilute H₂SO₄ add alcohol. To rest of the solution add NH₄OH in excess. Divide the NH₄OHmixed solution in two parts.

Procedure	Observation	Inference
(i) Potassium Ferrocyonide Test: To one part of the blue solution add acetic acid and potassium ferrocyoide.	A chocolate brown precipitate is formed.	Cu2+ is present.
(ii) Potassium Iodide Test: To another part add acetic acid and potassium iodide solution.	A white precipitate is formed in brown coloured solution.	Cu2+ is present

Result:-

Acidic radical: SO₄^2-

Basic radical: Cu²⁺

Therefore, The given salt is CuSO₄.