11. To analyse the acidic and basic radicals for a given salt (CuCO3).

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

Physical Appearance:-

Colour: Blue or bluish green.

Smell: Odourless.

Appearance: Amorphous.

Dry heating test:-

Procedure	Observation	Inference
Take a small amount of dry salt and heat it.	Colourless and odourless gas.	CO32- may be present.
	Salt becomes brown or black on heating.	Cu2+ may be present.

Flame test:-

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

Dilute sulfuric acid test:-

Procedure	Observation	Inference
Take a small quantity of the salt in a test tube and add 1-2 ml of dilute sulfuric acid.	Colourless, odourless gas with brisk effervescences is evoked which turns lime water milky.	CO32- may be present.

Confirmation of acid radicals by wet test:-

Aqueous solution or water solution: Shake a little of the salt with water. If the salt dissolves, this aqueous solution obtained is used for the wet test of acid radicals and is called water extract or 'W.E'.

Confirmation of carbonate (CO₃^2-):-

Procedure	Observation	Inference
Dilute HCL test to one portion of the solution add dilute HCL.	Brisk effervescence evolution of colourless and odourless gas turns lime water milky.	CO32- is present.

Wet test for basic radicals (cations):-

Preparation of solution for wet test for basic radicals:- If the salt is insoluble in distilled water as well as dilute HCL try to dissolve in concentrated HCL first in cold water and then on heating. The clear solution so obtained is original solution.

Analysis of group zero:-

Procedure	Observation	Inference
The solid is heated with concentrated solution of NaOH.	No gas evolved.	Group zero 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 to group 2:-

Procedure	Observation	Inference
Take about 2ml of solution on a test tube.	Black precipitate is formed.	Group 2  absent.

  

Confirmation for (Cu²⁺):-

Heat the black precipitate with aluminium quantity (1-2)ml of 50% HNO₃, precipitate dissolves. To one part of the solution add dilute H₂SO₄ and alcohol. To rest of the solution add NH₄OH in excess. 

Divide the NH₄OH mixed solution in two parts.

Procedure	Observation	Inference
(i) Potassium ferrocyonide test:- To one part of the blue solution add acetic acid and potassium ferrocyonide.	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 radicals: CO₃^2-

Basic radicals: Cu²⁺

Therefore, the given salt is CuCO₃.