a) `n_{K_2O} = (56,4)/(94) = 0,6 (mol)`
PTHH: `K_2O + H_2O -> 2KOH`
`n_{KOH} = 2n_{K_2O} = 1,2 (mol)`
`=> C_{M(KOH)} = (1,2)/(0,5) = 2,4M`
b) `HCl + KOH -> KCl + H_2O`
`n_{HCl} = n_{KOH} = 1,2 (mol)`
`=> V_{ddHCl} = (1,2.36,5)/(10%.1,198) = 365,61 (ml)`