Question

In the conversion of $Br_2$ to $BrO^-_3$, the oxidation number of $Br$ changes from

• A. zero to + 5
• B. + 1 to + 5
• C. zero to -3
• D. +2 to + 5

Answer 1

Answer: (A)

zero to + 5

Answer 2

Bromine has zero oxidation state because it is in free state

$B\overset{0}{r_{2}} \to BrO^{-}_{3}$
$\overset{x}{Br}\overset{-2}{O^{-}_{3}}$
$x + (-2 \times 3 ) = - 1$
$x + (-6) = - 1$
$x = + 6 -1$
$= + 5$

So, oxidation number changes from 0 to +5.