pH = 8.23
Reaction
HNO₂+KOH⇒KNO₂+H₂O
mol HNO₂ = 50 x 0.2 = 10 mlmol
mol KOH = 0.4 x 25 = 10 ml mol
Both of them completely react, resulting in hydrolysis salt which is composed of weak acids and strong bases
Formula :
[tex]\tt [OH^-]=\sqrt{\dfrac{Kw}{Ka}.M }[/tex]
Kw = water constant = 10⁻¹⁴
Ka = 4.6 x 10⁻⁴
M = anion (salt) concentration =
[tex]\tt \dfrac{mol~KNO_2}{total~volume}=\dfrac{10}{50+25}=0.133~M[/tex]
[tex]\tt [OH^-]=\sqrt{\dfrac{10^{14}}{4.6\times 10^{-4}} }\times 0.133\\\\(OH^-)=1.7\times 10^{-6}\\\\pOH=6-log~1.7=5.77\\\\pH+pOH=14\\\\pH+5.77=14\\\\pH=8.23[/tex]
