Write down the formula and chemical name of lime water.

Balance the following equation by Hit and trial method :

$\mathrm{Si} + \mathrm{NaOH} + {\mathrm{H}}_2\mathrm{O} \to {\mathrm{Na}}_2{\mathrm{SiO}}_3 + {\mathrm{H}}_2$

Balance the following equation by Hit and trial method :

${\mathrm{Na}}_2{\mathrm{CO}}_3 + \mathrm{HCl} \to \mathrm{NaCl} + {\mathrm{CO}}_2 + {\mathrm{H}}_2\mathrm{O}$

Balance the following equation by Hit and trial method :

${\mathrm{Na}}_2{\mathrm{CO}}_3 + {\mathrm{CO}}_2 + {\mathrm{H}}_2\mathrm{O} \to {\mathrm{NaHCO}}_3$

Balance the following equation by Hit and trial method :

$\mathrm{Mg} + {\mathrm{HNO}}_3 \to \mathrm{Mg}{\left({\mathrm{NO}}_3\right)}_2 + {\mathrm{H}}_2$