Question

\[A{\text{ }}\left( {black} \right) + {\text{dil}}{\text{. }}{{\text{H}}_2}S{O_4}\xrightarrow{{}}B\left( g \right) + C\](light green colour solution). Gas \[B\]turns lead acetate paper black. \[A,{\text{ }}B\] and \[C\] are respectively:
A. \[FeS,{\text{ }}{{\text{H}}_2}S{\text{ and FeS}}{{\text{O}}_4}\]
B. \[FeS,{\text{ FeS}}{{\text{O}}_4}{\text{ and }}{{\text{H}}_2}S\]
C. \[FeS{O_4},{\text{ FeS and }}{{\text{H}}_2}S\]
D. None of the above

Answer 1

Hint: Lead acetate is a white crystalline compound. The reaction shown in the question is a displacement reaction in which more reactive metal displaces a less reactive metal.

Complete step by step answer:
When ferrous sulphide reacts with dil. \[{H_2}S{O_4}\] to give hydrogen sulphide and ferrous sulphate.
Ferrous sulphide is black in colour.
\[\mathop {FeS}\limits_{Ferrous{\text{ sulphide}}} + \mathop {dil.{\text{ }}{{\text{H}}_2}S{O_4}}\limits_{\left( {Sulphuric{\text{ acid}}} \right)} \xrightarrow{{}}\mathop {{H_2}S}\limits_{\left( \begin{subarray}{l}
  Hydrogen \\
  Sulphide
\end{subarray} \right)} + \mathop {FeS{O_4}}\limits_{\left( \begin{subarray}{l}
  Ferrous \\
  Sulphate
\end{subarray} \right)} \]
After reaction the solution is light green color due to the presence of\[FeS{O_4}\]. \[{H_2}S\] gas turns lead acetate paper black.
Hence \[\left( A \right)\] is ferrous sulphide \[\left( {FeS} \right),\]\[\left( B \right)\] is Hydrogen sulphide \[\left( {{H_2}S} \right)\] and \[\left( C \right)\;\] is ferrous sulphate \[\left( {FeS{O_4}} \right)\].

Hence the correct option is (A).

Additional information: Ferrous sulphide is widely used in the steel industry for sulphur addition in metal during the manufacturing process. It also stimulates the mechanical properties of metal. Ferrous sulphate in their different hydrated states are light green, odourless and crystal solid. Anhydrous ferrous sulphate has a melting point of $680^\circ $C, however it decomposes over $300^\circ $ C, its density is $1.898gm{l^{ - 1}}.$ All ferrous sulphate salts are soluble in water.

Note:
Hydrogen sulphide is the chemical compound with the formula \[{H_2}S.\] It is colourless gas with the characteristic foul odour of rotten eggs. The ferrous can be obtained by the heating of the iron and sulfur. It is a black color solid. Iron sulfate is also known as green vitriol and it is the cheapest iron supplement.