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.

(a) What type of substance is B ?
(b) What type of substance is C ?
(c) Name the gas (i) D, and (ii) E ?
(d) State one characteristic property of gas D.
(e) Write one test to identify gas .E

Answer 1

(a) Here, iron powder and sulphur powder are mixed together. B is a mixture (Fe + S).

(b) Here, iron powder and sulphur powder are mixed together and heated strongly on a burner. So, C is the compound iron sulphide(FeS).

(c) (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

(d) Gas D smells like rotten egg.

(e) 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.