Question

How would you distinguish between the following pairs of substances on the
basis of the chemical tests given in brackets?
(1) Sodium Chloride and Potassium Chloride (flame test)
(ii) Zinc Carbonate and Lead Carbonate (dry heating)​

Answer 1

We can distinguish

(1) Sodium Chloride and Potassium Chloride (flame test)

(ii) Zinc Carbonate and Lead Carbonate (dry heating)​

as shown below.

(1) Due to the presence of sodium ions in NaCl, on performing the flame test, the flame colour turns golden yellow.

In KCl, due to the presence of potassium ions, the flame colour turns lilac.

(2) ZnCO₃ on heating gives ZnO, which is yellow when hot and white when cold. Whereas,

PbCO₃ on heating gives ZnO, which is buf when hot and orange when cold.

ZnCO₃ + Heat → ZnO + CO₂

PbCO₃ + Heat → PbO + CO₂