Question

Which of the following aqueous solutions produces metal after electrolysis?
\[(i){\text{ }}{{\text{K}}_2}C{r_2}{O_7}\]
\[(ii){\text{ KMn}}{O_4}\]
\[(iii){\text{ C}}{{\text{H}}_3}COONa\]
\[(iv){\text{ CuC}}{{\text{l}}_2}\]

Answer 1

Hint: When the electricity is passed through the aqueous solution of the chemical compounds then the decomposition of cations and anions takes place. The decomposed anion or cation gets collected near electrodes respectively. The metal which is cation gets deposited at the cathode and hence we get the metal. We will find the electrolysis products of each compound respectively.

Complete answer:
\[(i){\text{ }}{{\text{K}}_2}C{r_2}{O_7}\]
When the electric current is passed through the aqueous solution of potassium dichromate then we get the chromium oxide at cathode which is \[Cr{O_3}\]. Hence we do not get any metal electrolysis of aqueous solution of \[{{\text{K}}_2}C{r_2}{O_7}\].
\[(ii){\text{ KMn}}{O_4}\]
When the electric current is passed through the aqueous solution of potassium permanganate then we get manganese oxide at cathode which is \[MnO\]. Hence we do not get any metal of electrolysis of aqueous solution of \[{\text{KMn}}{O_4}\].
\[(iii){\text{ C}}{{\text{H}}_3}COONa\]
When the electric current is passed through the aqueous solution of ethanoate ion then we get methane gas at cathode which is\[C{H_4}\]. Hence we do not get any metal electrolysis of aqueous solution of \[{\text{C}}{{\text{H}}_3}COONa\].
\[(iv){\text{ CuC}}{{\text{l}}_2}\]
When the electric current is passed through the aqueous solution of copper chloride then we get copper at cathode which is\[Cu\]. Hence we get metal on electrolysis of aqueous solution of \[{\text{CuC}}{{\text{l}}_2}\].

Hence the correct option is \[(iv){\text{ CuC}}{{\text{l}}_2}\].

Note:
On electrolysis we get the reduced product of the aqueous solution. All the products formed above after electrolysis are reduced products. Hence we can also predict the product formed at cathode by finding the reduced form of the compound. The copper metal which is formed is pure in nature.