Q68 / 197 · NEET 2009 (Mains) · Chemistry

In the reaction $$ \mathrm{BrO}_3^{-}(\mathrm{aq})+5 \mathrm{Br}^{-}(\mathrm{aq})+6 \mathrm{H}^{+} \rightarrow 3 \mathrm{Br}_2(l)+3 \mathrm{H}_2 \mathrm{O}(l) $$ The rate of appearance of bromine $\left(\mathrm{Br}_2\right)$ is related to rate of disappearance of bromide ions as following

  • A
    $\frac{\mathrm{d}\left(\mathrm{Br}_2\right)}{\mathrm{dt}}=\frac{3}{5} \frac{\mathrm{d}\left(\mathrm{Br}^{-}\right)}{\mathrm{dt}}$
  • Correct answer
    B
    $\frac{\mathrm{d}\left(\mathrm{Br}_2\right)}{\mathrm{dt}}=-\frac{3}{5} \frac{\mathrm{d}\left(\mathrm{Br}^{-}\right)}{\mathrm{dt}}$
  • C
    $\frac{\mathrm{d}\left(\mathrm{Br}_2\right)}{\mathrm{dt}}=-\frac{5}{3} \frac{\mathrm{d}\left(\mathrm{Br}^{-}\right)}{\mathrm{dt}}$
  • D
    $\frac{\mathrm{d}\left(\mathrm{Br}_2\right)}{\mathrm{dt}}=\frac{5}{3} \frac{\mathrm{d}\left(\mathrm{Br}^{-}\right)}{\mathrm{dt}}$

Solution

$$ \begin{aligned} & -\frac{1}{4} \frac{\mathrm{d}\left(\mathrm{Br}^{-}\right)}{\mathrm{dt}}=-\frac{1}{3} \frac{\mathrm{d}\left(\mathrm{Br}_2\right)}{\mathrm{dt}} \\ & \frac{\mathrm{d}\left(\mathrm{Br}_2\right)}{\mathrm{dt}}=-\frac{3}{5} \frac{\mathrm{d}\left(\mathrm{Br}^{-}\right)}{\mathrm{dt}} \end{aligned} $$

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

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