The correct option is A 1 : 5
The unbalanced chemical equation is
BrO−3(aq)+Br−(aq)+H+(aq)→Br2(l)+H2O
The oxidation number of bromine increases from -1 (in Br− ion) to 0 (in Br2 ).
Increase in the oxidation number is 1.
The oxidation number of bromine decreases from +5 (in BrO−3 ) to 0 (in Br2 ).
Decrease in the oxidation number of bromine is 5.
Balance increase in oxidation number with decrease in oxidation number.
BrO−3(aq)+5Br−(aq)+H+(aq)→3Br2(l)+H2O
Hence, the ratio of BrO−3 to Br− is 1: 5.