Question

When the half-reactions Br2 + 2e– → 2Br– and Na → Na+ + e– are combined, the balanced redox equation is _____.

Answer 1

Since in the reduction of Br2 half-reaction 2 electrons are consumed and in the oxidation of sodium only one electron is produced, to balance the redox equation the sodium half equation must be multiplied by 2, giving:
Br2 + 2Na + 2e- --> 2Na+ + 2Br- + 2e-
The electrons act as spectator ions and can therefore be omitted from the final equation:
Br2 + 2Na --> 2Na+ + 2Br-

Answer 2

Explanation:

It is known that when there is gain of electrons then that is reduction reaction. Whereas when there is removal of electrons then that is oxidation reaction.

The given half reactions are as follows.

Reduction half-reaction: $Br_{2} + 2e^{-} \rightarrow 2Br^{-}$  ..... (1)

Oxidation half-reaction: $Na \rightarrow Na^{+} + e^{-}$ ...... (2)

Balancing the oxidation half reaction by multiplying it by 2 as follows.

Oxidation half-reaction: $2Na \rightarrow 2Na^{+} + 2e^{-}$ ..... (3)

Therefore, adding equation (1) and (3) by cancelling common terms, we get the balanced redox equation as follows.

          $2Na + Br_{2} \rightarrow 2Na^{+} + 2Br^{-}$