Question

Identify the substance underlined in each of the following:

The electrode that increases in mass during the electro-refining of silver.

Answer 1

Electro-refining of silver: The process in which impure metal is converted into the pure metal with the help of electric current is considered an electro-refining process.

• For the purification of silver metal, we take a container in which two electrodes are connected such as an anode and cathode.
• Anode plate is made up of impure silver and it is thick, showing the oxidation process [ the process in which metals lose electrons called oxidation process]. $$\begin{gathered} \mathrm{Oxidation}\mathrm{reaction}\mathrm{at}\mathrm{anode}: \\ \mathrm{Ag}\left(\mathrm{s}\right)\to {\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{e}}^{-} \end{gathered}$$
• The cathode plate is made up of pure silver and it is thin, showing the reduction process [the process in which substances gain electrons called the reduction process].
• $$\begin{gathered} \mathrm{Reduction}\mathrm{reaction}\mathrm{at}\mathrm{cathode}: \\ {\mathrm{Ag}}^{+}\left(\mathrm{aq}\right)+{\mathrm{e}}^{-}\to \mathrm{Ag}\left(\mathrm{s}\right) \end{gathered}$$
• Mass of the cathode increases as ${\mathrm{Ag}}^{+}$ gets deposited at the cathode while the mass of the anode gets reduced because ${\mathrm{Ag}}^{+}$it releases.

Thus, the mass of the cathode increases, and the substance is pure silver, $\mathrm{Ag}$.