Question

When Sodium amalgam (an alloy with mercury) is dipped into cold water, what reaction takes place?

Answer 1

1. When Sodium amalgam($\mathrm{NaHg}$) (an alloy with mercury) is dipped into cold water, Hydrogen(${\mathrm{H}}_2$) gas is liberated which can be easily collected.
2. Here, Mercury($\mathrm{Hg}$) in Sodium amalgam acts as a catalyst.
3. The reaction can be given as: $$\begin{gathered} 2\mathrm{NaHg}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+2\mathrm{Hg}\left(\mathrm{l}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right) \\ (\mathrm{Sodium}\mathrm{amalgam})\left(\mathrm{Water}\right)(\mathrm{Sodium}\mathrm{hydroxide})\left(\mathrm{Mercury}\right)(\mathrm{Hydrogen}\mathrm{gas}) \end{gathered}$$.