Question

Yellow ammonium sulphide solution is a suitable reagent used for the separation of:
\[
  A.{\text{ }}HgS{\text{ and }}PbS \\
  B.{\text{ }}PbS{\text{ and }}B{i_2}{S_3} \\
  C.{\text{ }}B{i_2}{S_3}{\text{ and }}CuS \\
  D.{\text{ }}CdS{\text{ and }}A{s_2}{S_3} \\
 \]

Answer 1

Hint- In order to deal with this question first we will know about the term reagent then we will proceed further by discussing yellow ammonium sulphide solution according to its property we will define our answer.

Complete step-by-step answer:
A reagent is a product or compound that is applied to a device to induce a chemical reaction or that is applied to the process if a reaction takes place. The terms reactant and reagent are also used interchangeably — but more precisely, a reactant is a product absorbed after a chemical reaction. Solvents are typically not labeled reactants since they are active in the reaction.
Now we will talk about yellow ammonium sulphide
As we know yellow ammonium sulphide is a solution (liquid).
Yellow ammonium sulphide solution is a suitable reagent used for the separation of \[CdS{\text{ and }}A{s_2}{S_3}\]as \[A{s_2}{S_3}\] is soluble in yellow ammonium sulphide and the colour of the solution is yellow, this indicates the presence of \[A{s^{3 + }}\] ions.
Hence, Yellow ammonium sulphide solution is a suitable reagent used for the separation of \[CdS{\text{ and }}A{s_2}{S_3}\]
So, the correct answer is option D.

Additional Information- The reaction does not use catalysts, so they are not reactants. In biochemistry the reactants are commonly called substrates, particularly in connection with enzyme-catalyzed reactions. Reducing the reagent (or reducing the reactant or limiting agent) in a chemical reaction is the product that is absorbed entirely before the chemical reaction is complete.

Note- This reagent limits the amount of substance produced, as the reaction cannot proceed without it. Where one or more other reagents surpass the amounts required to react with the limiting reagent, they are defined as excess reagents or excess reactants.