a, $Na_{2}O$ $+^{}$ $H_{2}O $ $^→{}$ $2NaOH^{}$
$2NaOH+CO_{2}→H$$_{2}O+$ $Na_{2}$$CO_{3}$
$Na_{2}$$CO_{3}+$ $HCl_{}$ → $NaCl_{} +$$NaHCO_{3}$
$2NaCl_{}$ $+ 2H_{2}O$ → $Cl_{2}↑ + $$H_{2}↑+2NaOH$
b,
$K_{2}O$ $+ H_{2}O→2KOH$
$KOH+KHCO_{3}→$ $H_{2}O$ $+K_{2}$$CO_{3}$
$2HCl_{}$ $+ K_{2}CO$$_{3}$ $→2KCl_{}$ $+H_{2}O$ $+CO_{2}↑$
$2KCl_{}$ $+2H_{2}O$ $→2KOH_{}$ $+Cl_{2}$ $+H_{2}$