Question

Consider the following reaction in aqueous solution.
$5 Br ^{-}(a q)+ BrO _{3}{ }^{-}(a q)+6 H ^{+}(a q) \underset{+3 H _{2} O (l)}{\longrightarrow }$
If the rate of appearance of $Br _{2}$ at a particular moment during the reaction is $0.025\, Ms ^{-1}$, what is the rate of disappearance (in $Ms ^{-1}$ ) of $Br ^{-}$at that moment?

• A. $0.025\, ms ^{-1}$
• B. $0.042\, ms ^{-1}$
• C. $0.075\, ms ^{-1}$
• D. $0.125\, ms ^{-1}$

Answer 1

Answer: (B)

The two rates are related as
$\left.-\frac{1}{5} \frac{d\left[ Br ^{-}\right]}{d t}=\frac{1}{3} \frac{d\left[ Br _{2}\right]}{d t}\right]$
$-\frac{d\left[ Br ^{-}\right]}{d t}=\frac{5}{3} \frac{d\left[ Br _{2}\right]}{d t}$
$=\frac{5}{3} \times 0.025=0.042\, Ms ^{-1}$