Question

Q. Select the letter A to H for the correct answer corresponding to the statement.

A. Ammoniacal $\mathbf{CuCl}$ B. Trichloromethane

C. Trichloroethane D. Bromine solution

E. Aqueous $\mathbf{KOH}$ F. Ethene

G. Soda-lime H. Ethyne

The reagent which can distinguish between Ethene and Ethyne.

Answer 1

1. Ammoniacal copper chloride is a mixture of solid Copper (I) chloride dissolve in water with Ammonia.
2. The solution formed is blue in colour.
3. Ethyne, when react with Ammoniacal copper (I) chloride or cuprous chloride, forms a precipitate Cuprous acetylide which is red in colour and Ammonium chloride.
4. The reaction is shown below.

$$\begin{gathered} \mathrm{CH}\equiv \mathrm{CH}\left(g\right)+2\mathrm{CuCl}\left(\mathrm{aq}\right)+2{\mathrm{NH}}_3\left(\mathrm{aq}\right)\to {\mathrm{Cu}}_2{\mathrm{C}}_2\left(s\right)+2{\mathrm{NH}}_4\mathrm{Cl}\left(\mathrm{aq}\right) \\ \mathrm{Ethyne}\mathrm{Cuprous}\mathrm{Ammonia}\mathrm{Cuprous}\mathrm{Ammonium} \\ \mathrm{chloride}\mathrm{acetylide}\mathrm{chloride} \end{gathered}$$

3. Ethene shows no reaction with Ammoniacal cuprous chloride.

$$\begin{gathered} {\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2\left(g\right)+\mathrm{CuCl}\left(\mathrm{aq}\right)+{\mathrm{NH}}_3\left(\mathrm{aq}\right)\to \mathrm{No}\mathrm{reaction} \\ \mathrm{Ethene}\mathrm{Cuprous}\mathrm{Ammonia} \\ \mathrm{Chloride} \end{gathered}$$

4. Therefore, the reagent which can distinguish between Ethene and Ethyne is Ammoniacal $\mathit{C}\mathit{u}\mathit{C}\mathit{l}$.

5. Hence, the correct answer corresponding to the statement is A.