Match (A) iron sulphide, (B) sodium thiosulphate, (C) calcium carbonate, (D) ammonium chloride, (E) concentrated sulphuric acid, (F) nitric acid, with its correct description given in (i) - (vi) below:
(i) It forms colloidal sulphur when treated with dilute hydrochloric acid. (ii) When it is heated with an alkali a gas is formed which produces white fumes with HCI. (iii) It reacts with acids and a gas having smell like rotten eggs is liberated. (iv) It gives a brisk effervescence when treated with dilute sulphuric acid. (v) It gives ring test. (vi) It oxidises sulphur to sulphur dioxide. 

Answer

To match the compounds with their correct descriptions, we will analyze each compound and its corresponding reaction or property.

### Step-by-Step Solution:

1. **Iron Sulphide (FeS)**:
- **Description**: It reacts with acids and a gas having a smell like rotten eggs is liberated.
- **Reaction**: FeS + 2 HCl → FeCl2 + H2S (gas)
- **Conclusion**: Matches with **(iii)**.

2. **Sodium Thiosulphate (Na2S2O3)**:
- **Description**: It forms colloidal sulphur when treated with dilute hydrochloric acid.
- **Reaction**: Na2S2O3 + 2 HCl → 2 NaCl + H2O + SO2 + Colloidal S
- **Conclusion**: Matches with **(i)**.

3. **Calcium Carbonate (CaCO3)**:
- **Description**: It gives brisk effervescence when treated with dilute sulphuric acid.
- **Reaction**: CaCO3 + H2SO4 → CaSO4 + H2O + CO2 (gas)
- **Conclusion**: Matches with **(iv)**.

4. **Ammonium Chloride (NH4Cl)**:
- **Description**: When it is heated with an alkali, a gas is formed which produces white fumes with HCl.
- **Reaction**: NH4Cl + NaOH (heat) → NaCl + H2O + NH3 (gas)
- **Conclusion**: Matches with **(ii)**.

5. **Concentrated Sulphuric Acid (H2SO4)**:
- **Description**: It oxidizes sulphur to sulphur dioxide.
- **Reaction**: H2SO4 + S → SO2 + H2O
- **Conclusion**: Matches with **(vi)**.

6. **Nitric Acid (HNO3)**:
- **Description**: It gives a ring test.
- **Conclusion**: Matches with **(v)**.

### Final Matching:
- (A) Iron Sulphide → (iii)
- (B) Sodium Thiosulphate → (i)
- (C) Calcium Carbonate → (iv)
- (D) Ammonium Chloride → (ii)
- (E) Concentrated Sulphuric Acid → (vi)
- (F) Nitric Acid → (v)