Answer: As part 'A' is heated, a compound FeS is formed by the reaction between iron filings and sulphur. When dilute HCI is added to part A, FeS will react with dil HCI to form H2S gas which has smell of rotten eggs and will turn lead acetate paper black.When dil, HCI is added to it, iron filings react with dill.

Introduction:
When dilute hydrochloric acid (HCl) is added to a mixture of iron filings (Fe) and sulphur powder (S), several chemical reactions occur. This reaction is an example of a combination reaction, where two or more substances combine to form a single new substance. In this case, the reaction results in the formation of iron(II) chloride (FeCl2) and hydrogen sulphide (H2S).

Reaction:
The reaction can be represented by the following chemical equation:
Fe + S + 2HCl → FeCl2 + H2S

Explanation:
1. Formation of Iron(II) Chloride (FeCl2):
The iron filings react with the hydrochloric acid to form iron(II) chloride. This occurs due to the displacement of hydrogen from the acid by the more reactive metal, iron. The iron(II) chloride is soluble in water and appears as a greenish-yellow solution.
Fe + 2HCl → FeCl2 + H2

2. Formation of Hydrogen Sulphide (H2S):
The sulphur powder reacts with the hydrochloric acid to produce hydrogen sulphide gas. This occurs due to the displacement of hydrogen from the acid by sulphur. Hydrogen sulphide is a toxic gas with a characteristic odor of rotten eggs.
S + 2HCl → H2S + Cl2

3. Observations:
- Effervescence: As the reaction occurs, effervescence is observed due to the evolution of hydrogen gas.
- Color change: The greenish-yellow color of the iron(II) chloride solution indicates the formation of the compound.
- Odor: The characteristic odor of hydrogen sulphide gas is noticeable.

4. Key points:
- Dilute hydrochloric acid reacts with iron filings and sulphur powder.
- Iron(II) chloride and hydrogen sulphide are formed as products.
- Iron displaces hydrogen from the acid, forming iron(II) chloride.
- Sulphur displaces hydrogen from the acid, forming hydrogen sulphide gas.
- Effervescence, color change, and odor are observable during the reaction.

In conclusion, when dilute hydrochloric acid is added to a mixture of iron filings and sulphur powder, a combination reaction occurs. This results in the formation of iron(II) chloride and hydrogen sulphide. The reaction is characterized by effervescence, color change, and the distinct odor of hydrogen sulphide gas.

When dilute hydrochloric acid is added to a mixture of iron filings and sulphur powder, a combination reaction occurs. This results in the formation of iron(II) chloride and hydrogen sulphide. The reaction is characterized by effervescence, color change, and the distinct odor of hydrogen sulphide gas.