$(i)$ Name the compound formed on heating a mixture of iron filings and sulphur.
$(ii)$ If dilute $HCl$ is added to the above compound,name the gas evolved and write down its two properties.

(N/A) $(i)$ When iron filings and sulphur are heated together,they undergo a chemical reaction to form iron$(II)$ sulphide,represented by the formula $FeS$.
$(ii)$ When dilute hydrochloric acid $(HCl)$ is added to iron$(II)$ sulphide $(FeS)$,a chemical reaction occurs to produce hydrogen sulphide gas $(H_2S)$.
The chemical equation is: $FeS(s) + 2HCl(aq) \rightarrow FeCl_2(aq) + H_2S(g)$.
Two properties of hydrogen sulphide $(H_2S)$ gas are:
$(a)$ It is a colourless gas.
$(b)$ It has a characteristic smell of rotten eggs.