pH of mixed solution = 4.3
Further explanation
A buffer solution is a solution that can maintain a good pH value due to the addition of a little acid or a little base or dilution.
The buffer solution can be acidic or basic
Acid buffer solution consists of weak acids and their salts.
[tex]\tt \displaystyle [H^+]=Ka\times\frac{mole\:weak\:acid}{mole\:salt\times valence}[/tex]
valence according to the amount of salt anion
mol CH₃COOH = 25 ml x 0.9 = 22.5 mlmol
mol NaOH = 25 ml x 0.45 = 11.25 mlmol
ICE method :
Reaction
NaOH + CH₃COOH ---> CH₃COONa + H₂O
11.25 22.5
11.25 11.25 11.25 11.25
11.25 11.25 11.25
mol acid = 11.25, mol salt = 11.25, Ka CH₃COOH = 5.10⁻⁵
Then [H⁺]=
[tex]\tt [H^+]=5.10^{-5}.\dfrac{11.25}{11.25\times 1}\rightarrow salt~valence=1\\\\(H^+]=5.10^{-5}\\\\pH=5-log5=4.3[/tex]
