The solubility of an ionic compound is maximum in

Softening of hard water can be done by:

a) Passing it through a cation exchange resin.

b) Passing it through hydrated aluminosilicate.

c) Adding washing soda to it.

Which of the following reactions is possible in a cation-exchanger in the synthetic resin method?

a. $2\mathrm{RH}\left(\mathrm{resin}\right)+{\mathrm{Ca}}^{2+}\to {\left(\mathrm{R}\right)}_2\mathrm{Ca}+2{\mathrm{H}}^{+}$

b. $\mathrm{R}-\stackrel{+}{\mathrm{N}}{\mathrm{H}}_3\stackrel{-}{\mathrm{O}}\mathrm{H}\left(\mathrm{resin}\right)+{\mathrm{Cl}}^{-}\to \mathrm{R}-\stackrel{+}{\mathrm{N}}{\mathrm{H}}_3{\mathrm{Cl}}^{-}+{\mathrm{OH}}^{-}$

c. ${\mathrm{H}}^{+}+{\mathrm{OH}}^{-}\to {\mathrm{H}}_2\mathrm{O}$

d. $2\mathrm{RNa}\left(\mathrm{s}\right)+{\mathrm{M}}^{+2}\left(\mathrm{aq}\right)\to {\mathrm{R}}_2\mathrm{M}\left(\mathrm{s}\right)+2{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)$