The correct option is A 3Br2(aq)+6OH−(aq)⟶5Br−(aq)+BrO−3(aq)+3H2O(l)
The unbalanced chemical equation is as follows:
Br2(aq)+OH−(aq)⟶Br−(aq)+BrO−3(aq)
All atoms other than H and O are balanced.
The oxidation number of Br changes from 0 to -1. The change in the oxidation number is 1.
The oxidation number of Br changes from 0 to +5. The change in the oxidation number is 5.
To balance the increase in the oxidation number with decrease in the oxidation number, multiply Br2 with 3 and Br− with 5.
3Br2(aq)+OH−(aq)⟶5Br−(aq)+BrO−3(aq)
To balance O atoms, add, two water molecules on LHS.
3Br2(aq)+OH−(aq)+2H2O⟶5Br−(aq)+BrO−3(aq)
To balance H atoms, add 5H+ on the RHS.
3Br2(aq)+OH−(aq)+2H2O⟶5Br−(aq)+BrO−3(aq)+5H+
Since the reaction occurs in basic medium, add 5OH− ions on both sides.
3Br2(aq)+6OH−(aq)+2H2O⟶5Br−(aq)+BrO−3(aq)+5H++5OH−
On RHS, five protons and five hydroxide ions forms five water molecules out of which two cancels out with two water molecules on RHS.
3Br2(aq)+6OH−(aq)⟶5Br−(aq)+BrO−3(aq)+3H2O(l)
This is the balanced chemical equation.