Iron filings and sulphur were mixed together and

1. In part A iron and sulphur will remain as such in the form of a mixture. On adding dilute hydrochlo-ride acid iron will react to evolve hydrogen gas. The gas can be tested by bringing a burning splinter near its mouth. It will burn with a pop sound.

$\mathrm{Fe}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{FeCl}_{2}(a q)+\mathrm{H}_{2}(g)$

2. In part ' $B$ ' iron and sulphur will combine on heating to form greyish black solid known as iron sulphide.

$\mathrm{Fe}(s)+5(s) \stackrel{\text { heat }}{\longrightarrow} \mathrm{FeS}(s)$

3. When dilute hydrocloric acid is added to the greyish black mass taken in a tube, a gas with foul smell similar to that of the rotton eggs will evolve. This is hydrogen sulphide $(\mathrm{H} 2 \mathrm{~S})$ Cover or Lid

$\mathrm{FeS}(s)+2 \mathrm{HCl}(a q) \longrightarrow \mathrm{FeCl}_{2}(a q)+\mathrm{H}_{2} \mathrm{~S}(g)$