3. To analyse the acidic and basic radicals in the given salt (PbCO3).

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

Physical Examination Test:-

Colour – White

Smell – Odourless

Appearance – Amorphous

Dry Heating Test:-

Procedure	Observation	Inference
Take a small amount of salt in dry test tube and heat.	A colourless and odourless gas is evolved.	CO32- or C2O42- may be present.
	Residue of salt is brown when hat and yellow when cold.	Pb2+ may be present.

Flame Test:-

Procedure	Observation	Inference
Prepare a paste of the salt with concentrated HCl acid on a clean watch glass. Place small amount of this paste on a platinum wire loop and introduce it into the flame.	Dull bluish-white with naked eye.	Pb2+ may be present.
	White through the blue glass.	Pb2+ may be present.

Dilute Sulfuric Acid Test:-

Procedure	Observation	Inference
Take a small amount of salt in attest tube and add 1-2 ml of dilute sulfuric acid.	Colourless, odourless gas with brisk effervescene, which turns lime water milky.	Gas evolved	Possible Radicals
		CO2	CO32-

Confirmation of Acid Radicals by Wet Tests:-

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 test of acid radicals and is called ‘Water Extract’ or ‘W.E’.

Procedure	Observation	Inference
Dilute HCl test: To one portion of the solution add dilute HCl.	Brisk effervescence and evolution of colourless, odourless gas, which turns lime water milky.	CO32- is present.
Magnesium sulfate test: Add magnesium sulfate to one portion of solution.	Formation of white precipitate.	CO32-  is present.

Analysis of Group 1 (Silver Group):-

Procedure	Observation	Inference
Original solution is prepared in water and dilute HCl is added to it. Filter and wash the precipitate, divide it into two parts.	White precipitate is formed.	Pb2+ may be present.
a) Add potassium iodide to the white precipitate of the first part.	Yellow precipitate is formed.	Pb2+ is present.
b) Add potassium chromate to the second part.	Yellow precipitate is formed.	Pb2+ is present.

Result:-

Acid radicals – CO₃^2-

Basic radicals – Pb²⁺

Therefore, the salt is lead carbonate PbCO₃.