Question

The reaction below was carried out in an acidic solution.

Upper I minus, plus upper I upper O minus subscript 3 right arrow upper I subscript 2.

Which statement is true about this equation?
Although it is unbalanced, it can be balanced by using the half-reaction method.
It has been balanced by using the half-reaction method.
It has been balanced by directly using spectator ions.
Although it is unbalanced, it can be balanced by directly using spectator ions.

Answer 1

Answer: Although it is unbalanced, it can be balanced by using the half-reaction method.

Reason: The equation as written is not balanced for O and charge. Using half-reactions in acidic solution gives

Oxidation: 2 I− → I2 + 2 e−
Reduction: 2 IO3− + 12 H+ + 10 e− → I2 + 6 H2O

Combining and simplifying yields the balanced equation
5 I− + IO3− + 6 H+ → 3 I2 + 3 H2O.