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 the 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 once characteristic property of gas D.

Answer 1

When mixture A(Iron + sulphur) is heated strongly, substance C is formed.

$\underset{\mathrm{A}}{\underbrace{\mathrm{Fe}+\mathrm{S}}}\stackrel{\mathrm{Heat}}{\to }\underset{\mathrm{C}}{\underbrace{\mathrm{FeS}}}$

When C(iron sulphide) reacts with dilute hydrochloric acid, a foul-smelling hydrogen sulphide gas(D) is eliminated.

$\underset{\mathrm{C}}{\underbrace{\mathrm{FeS}}}+2\mathrm{HCl}\to \underset{\mathrm{D}}{\underbrace{{\mathrm{H}}_2\mathrm{S}}}+{\mathrm{FeCl}}_2$

When dilute hydrochloric acid is added in mixture B(iron + sulphur), then only iron powder reacts with dilute hydrochloric acid and a colourless and odourless hydrogen gas evolves. It burns with a pop-up sound. Sulphur being non-metal do not react with dilute hydrochloric acid.

$\underset{\mathrm{B}}{\underbrace{2\mathrm{Fe}}}+6\mathrm{HCl}\to 2{\mathrm{FeCl}}_3+\underset{\mathrm{E}}{\underbrace{3{\mathrm{H}}_2}}$

(a) B is a mixture of iron and sulphur.

(b) Substance C is a black coloured compound known as iron sulphide.

(c) (i) D is hydrogen sulphide gas eliminated from mixture A.
(ii) E is hydrogen gas eliminated from mixture B.

(d) D(Hydrogen sulphide gas) smells like rotten eggs.