In the reaction BrO₃⁻(aq) + 5Br⁻(aq) + 6H⁺ → 3Br₂(l) + 3H₂O(l), the rate of appearance of bromine (Br₂) is…

In the reaction $BrO_3^-(aq) + 5Br^-(aq) + 6H^+ \rightarrow 3Br_2(l) + 3H_2O(l)$, the rate of appearance of bromine ($Br_2$) is related to rate of disappearance of bromide ions as following
A $\frac{d[Br_2]}{dt} = \frac{3}{5}\frac{d[Br^-]}{dt}$
B $\frac{d[Br_2]}{dt} = -\frac{3}{5}\frac{d[Br^-]}{dt}$
C $\frac{d[Br_2]}{dt} = -\frac{5}{3}\frac{d[Br^-]}{dt}$
D $\frac{d[Br_2]}{dt} = \frac{5}{3}\frac{d[Br^-]}{dt}$

Detailed Solution

For the given reaction: Rate $= -\frac{1}{5}\frac{d[Br^-]}{dt} = \frac{1}{3}\frac{d[Br_2]}{dt}$
The negative sign appears with $Br^-$ because its concentration decreases with time.
$\frac{1}{3}\frac{d[Br_2]}{dt} = -\frac{1}{5}\frac{d[Br^-]}{dt}$
$\frac{d[Br_2]}{dt} = -\frac{3}{5}\frac{d[Br^-]}{dt}$

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Practise Rate of a Chemical Reaction All 7 questions This chapter in 2009 AIPMT