Question

Calculate the pH when 25.0ml of 0.90M CH3COOH is mixed with 25.0ml of 0.45M NaOH.​

Answer 1

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.

`\tt \displaystyle [H^+]=Ka*(mole\:weak\:acid)/(mole\:salt* valence)`

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⁺]=

`\tt [H^+]=5.10^(-5).(11.25)/(11.25* 1)\rightarrow salt~valence=1\\\\(H^+]=5.10^(-5)\\\\pH=5-log5=4.3`