Question

Complete the following.

${\mathrm{CaCl}}_2+2{\mathrm{C}}_{17}{\mathrm{H}}_{35}{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}\to$

Answer 1

The complete chemical equation is

$\underset{\mathrm{Calcium}\mathrm{chloride}\mathrm{in}\mathrm{hardwater}}{{\mathrm{CaCl}}_2\left(\mathrm{s}\right)}+\underset{\mathrm{Sodium}\mathrm{stearate}(\mathrm{soap}\mathrm{soluble})}{2{\mathrm{C}}_{17}{\mathrm{H}}_{35}{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}\left(\mathrm{s}\right)}\to \underset{\mathrm{Calcium}\mathrm{stearate}(\mathrm{insoluble}\mathrm{soap})}{\mathrm{Ca}{\left({\mathrm{C}}_{17}{\mathrm{H}}_{35}\mathrm{COO}\right)}_2\left(\mathrm{s}\right)\downarrow }+\underset{\mathrm{sodium}\mathrm{chloride}}{2\mathrm{NaCl}\left(\mathrm{s}\right)}$

• This reaction represents the precipitate formation of soap in hard water.
• Hard water containing soluble salt of calcium or magnesium does not give lather with soap but gives precipitation instead.
• Here calcium chloride present in the hard water reacts with sodium stearate in the soap which is soluble in water giving a precipitate of calcium stearate which is insoluble in water.