Question

what is the oxidation number of bromine as a reactant and in the product? br in br₂ br in al₂br₆

Explanation:

Step1: Determine oxidation number in $Br_2$

In elemental form, the oxidation number of an element is 0. So in $Br_2$, the oxidation number of $Br$ is 0.

Step2: Determine oxidation number in $Al_2Br_6$

Aluminum ($Al$) has an oxidation - state of +3 in most of its compounds. Let the oxidation number of $Br$ be $x$. In $Al_2Br_6$, using the rule that the sum of oxidation numbers in a neutral compound is 0. For $Al_2Br_6$, we have $2\times(+3)+6x = 0$. Solving for $x$:
\[

$$\begin{align*} 6 + 6x&=0\\ 6x&=- 6\\ x&=-1 \end{align*}$$

\]

Answer:

The oxidation number of $Br$ in $Br_2$ is 0 and in $Al_2Br_6$ is - 1.