Question

A tarnished silver rod when kept in water containing magnesium bars regains its lustre. Justify.

Answer 1

• Lustre is the property of metal because of which it shined.
• A tarnished silver rod is not shiny in nature, and it is an oxidized form of silver.
• Tarnished silver(${\mathrm{Ag}}_2\mathrm{O}\left(\mathrm{s}\right)$) when dipped in water containing magnesium results in the formation of Magnesium dioxide(MgO) and lustrous silver metal(Ag).
• It is a type of displacement reaction.
• Displacement reaction: It is the type of reaction in which a more reactive metal will displace a less reactive metal.
• Magnesium is more reactive than silver.
• There can easily displace it and results in the formation of lustrous silver.
• $\underset{\mathrm{Silver}\mathrm{Oxide}}{{\mathrm{Ag}}_2\mathrm{O}\left(\mathrm{s}\right)}+\underset{\mathrm{Magnesium}}{\mathrm{Mg}\left(\mathrm{s}\right)}\to \underset{\mathrm{Magnesium}\mathrm{Oxide}}{\mathrm{MgO}\left(\mathrm{s}\right)}+2\underset{\mathrm{Silver}}{\mathrm{Ag}\left(\mathrm{s}\right).}$