Q80 / 160 · JIPMER 2005 · Chemistry

$\mathrm{NaOH}(a q), \mathrm{HCl}(a q),$ and $\mathrm{NaCl}(a q)$ concentration of each is $10^{-3} \mathrm{M}$. Their pH will be respectively

  • A
    $10,6,2$
  • Correct answer
    B
    $11,3,7$
  • C
    $10,3,7$
  • D
    $10,4,7$

Solution

Given $\mathrm{OH}^{-}$ion conc. is $10^{-3} \mathrm{M}$ we know $\left[\mathrm{H}^{+}\right]\left[\mathrm{OH}^{-}\right]=10^{-14}$ $\begin{array}{cc}\text { or } & {\left[\mathrm{H}^{+}\right]=\frac{10^{-14}}{10^{-3}}} \\ \text { or } & {\left[\mathrm{H}^{+}\right]=10^{-11}} \\ \because & \mathrm{pH}=-\log \left[\mathrm{H}^{+}\right]=-\log \left[10^{-11}\right]\end{array}$ Similarly pH of HCl is 3 and pH of NaCl is 7.

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

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