2Na + 2H2O → 2NaOH + H2↑
\(n_{Na}=\dfrac{7,75}{23}=\dfrac{31}{92}\left(mol\right)\)
Theo PT: \(n_{NaOH}=n_{Na}=\dfrac{31}{92}\left(mol\right)\)
\(\Rightarrow C_{M_{NaOH}}=\dfrac{31}{92}\div0,25=1,35\left(M\right)\)
nNa2O = \(\dfrac{7,75}{62}\) =0,125 mol
PTHH: Na2O + H2O --------> NaOH
Na2O + H2O -> 2NaOH
nNaOH=2. Na2O= 2.0,125=0,25(mol)