Question

Iron powder and sulphur powder were mixed together and divided into two parts A and B. When part A was heated strongly over a burner, then a substance C was formed. The part B was, however, not heated at all. When dilute hydrochloric acid was added to substance C, then gas D was evolved and when dilute hydrochloric acid was added to part B then gas E was evolved.

1. What type of substance is B ?
2. What type of substance is C ?
3. Name the gas (i) D, and (ii) E ?
4. State one characteristic property of gas D.
5. Write one test to identify gas E.

Answer 1

1. Here, iron powder and sulphur powder are mixed together. B is a mixture (Fe + S).
2. Here, iron powder and sulphur powder are mixed together and heated strongly on a burner. So, C is the compound iron sulphide(FeS).
3. i. Here, dilute HCl was added to C (iron sulphide)to obtain D, which is hydrogen sulphide gas.           
   FeS + 2HCl → FeCl₂ + H₂S
   ii. When dilute HCl is added to B, Fe present in the mixture reacts with the acid to form hydrogen gas.
   Fe + HCl → FeCl₂ + H₂
4. Gas D smells like rotten egg.
5. When a burning stick is held in the gas, the gas itself catches fire with blue flame and a ‘pop’ sound. In the process, the burning stick extinguishes.