Question

Name three metals which react with cold water to form hydrogen gas. Support your answer with fully balanced chemical equations.

Answer 1

The highly reactive metals react with cold water. The three metals which react with cold water to form Hydrogen gas $\left({\mathrm{H}}_2\right)$are:

• Sodium $\left(\mathrm{Na}\right)$

$2\mathrm{Na}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{NaOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

• Potassium $\left(\mathrm{K}\right)$

$2\mathrm{K}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to 2\mathrm{KOH}\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

• Calcium $\left(\mathrm{Ca}\right)$

$\mathrm{Ca}\left(\mathrm{s}\right)+2{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to \mathrm{Ca}{\left(\mathrm{OH}\right)}_2+{\mathrm{H}}_2\left(\mathrm{g}\right)$

The moderately reactive metals react with hot water to form metal hydroxide (example: Magnesium $\left[\mathrm{Mg}\right]$) and the less reactive metals react with steam to form metal oxide (example: Zinc $\left[\mathrm{Zn}\right]$, Iron $\left[\mathrm{Fe}\right]$, Aluminium $\left[\mathrm{Al}\right]$).