`#AkaShi`
`Na_2O + H_2O -> 2NaOH`
`n_{Na_2O}=31/62=0,5 (mol)`
`⇒n_{NaOH}=2xx0,5=1 (mol)`
`⇒m_{NaOH}=1xx40=40 (g)`
`m_{dd sau pư}=31+169=200`
`⇒C%_{NaOH}=40/200xx100%=20%`
...............
b) `2NaOH + CO_2 -> Na_2CO_3 + H_2O`
`n_{CO_2}=1/2=0,5 (mol)`
`⇒V_{CO_2}=0,5xx22,4=11,2 (l)`