MCQ
$pH$ of a solution of $10\,ml$. $1\,N $ sodium acetate and $50\,ml$ $2\,N$  acetic acid $({K_a} = 1.8 \times {10^{ - 5}}),$ is approximately
  • $4$
  • B
    $5$
  • C
    $6$
  • D
    $7$

Answer

Correct option: A.
$4$
(a)$pH = p{K_a} + {\rm{log}}\frac{{{\rm{[Salt]}}}}{{{\rm{[Acid]}}}}$

$pH = - \log \,(1.8 \times {10^{ - 5}}) + \log \frac{{[10]}}{{[100]}}$

$ = - \log \,\,1.8 + 5 + \log \,\,{10^{ - 1}}$

$ = - \;0.2553 + 5 - 1 = 3.7447\,\,\,{\rm{or}}\,\, = 4$

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