Q52 / 180 · AIIMS 2002 · Chemistry

The $\mathrm{pH}$ of solution containing $0.10 \mathrm{M}$ sodium acetate and $0.03 \mathrm{M}$ acetic acid is $\left(\mathrm{p} K_a\right.$ for $\left.\mathrm{CH}_3 \mathrm{COOH}=4.57\right)$

  • A
    4.09
  • B
    6.09
  • Correct answer
    C
    5.09
  • D
    7.09

Solution

According to Henderson's equation, $$ \begin{aligned} & \mathrm{pH}=\mathrm{p} K_a+\log \frac{[\text { salt }]}{[\text { acid }]} \\ & \mathrm{CH}_3 \mathrm{COOH}+\mathrm{NaOH} \rightarrow \mathrm{CH}_3 \mathrm{COONa}+\mathrm{H}_2 \mathrm{O} \end{aligned} $$ Putting the values, we get : $$ \begin{aligned} \mathrm{pH} & =4.57+\log \frac{0.10}{0.03} \\ \Rightarrow \quad \mathrm{pH} & =5.09 \end{aligned} $$

Hence, the correct answer is option: 'C'.

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