MCQ
What will be the $pH$ of a solution formed by mixing $40\,\,ml$ of $0.10\,\,M\,\,HCl$ with $10\,\,ml$ of $0.45\,\,M\,\,NaOH$
  • $12$
  • B
    $10$
  • C
    $8$
  • D
    $6$

Answer

Correct option: A.
$12$
(a) M.eq. of $0.10$ $M\,\,HCl = \frac{{0.10}}{{1000}} \times 40 = 0.004\,M$

M.eq. of $0.45$  $M\,\,NaOH = \frac{{0.45 \times 10}}{{1000}} = 0.0045\,M$

Now left $[O{H^ - }] = 0.0045 - 0.004$$ = 5 \times {10^{ - 4}}$ $M$

Total volume $ = 50 \,ml.$

$[O{H^ - }] = \frac{{5 \times {{10}^{ - 4}}}}{{50}} \times 1000$; $[O{H^ - }] = 1 \times {10^{ - 2}}$

$pOH = 2 ; pH = 14 -pOH = 12.$

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