Besar oh dlm 10ml larutan yg mengandung 9,5 gram kno 2

Diketahui :
m KNO₂ = 9,5 g
v = 10 mL = 0,01 L
Mr KNO₂ = 39 + 14 + (2 × 16) = 85 g/mol
Ditanya :
pH ?
Jawab :
n KNO₂ = m KNO₂ × Mr KNO₂
n KNO₂ = [tex] \frac{9,5 g}{85 g/mol} [/tex]
n KNO₂ = 0,1118 mol

KNO₂ + H₂O → KOH + HNO₂
n OH⁻ = n KOH = n KNO₂ = 0,1118 mol
[OH⁻] = [tex] \frac{0,1118 mol}{0,01 L} [/tex]
[OH⁻] = 11,18 M

pOH = -log [OH⁻]
pOH = -log 11,18
pOH = - 1,05

pH = pKw - pOH
pH = 14 - (-1,05)
pH = 14 + 1,05
pH = 15,5