Q61 / 180 · JIPMER 2017 · Chemistry

When 750 mL of 0.5 M HCl is mixed with 250 mL of 2 M NaOH solution, the value of pH will be

  • A
    $\mathrm{pH}=7$
  • Correct answer
    B
    $\mathrm{pH}\gt7$
  • C
    $\mathrm{pH} \lt 7$
  • D
    $\mathrm{pH}=0$

Solution

$\begin{aligned}n_{\mathrm{HCl}} & =M_{\mathrm{HCl}} \times V_{\mathrm{HCl}} \text { and } \\ n_{\mathrm{NaOH}} & =M_{\mathrm{NaOH}} \times V_{\mathrm{NaOH}} \end{aligned}$ where, $n=$ number of moles $\begin{aligned}& M=\text { molarity, } V=\text { volume } \\ & \therefore n_{\mathrm{HCl}}=0.5 \times 750=375 \text { milimoles. } \\ & n_{\mathrm{NaOH}}=2.0 \times 250=500 \text { milimoles. } \\ & \because n_{\mathrm{NaOH}} \gt n_{\mathrm{HCl}} \end{aligned}$ The solution is basic and has $\mathrm{pH} \gt 7$.

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

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