In which of the following reactions `H_2O_2` acts as a reducing agent?
`i) H_2O_2 + 2H^(+) + 2e^(-) to 2H_2O " " ii) H_2O_2 - 2e^(-) to O_2 + 2H^(+)`
`iii) H_2O_2 + 2e^(-) to 2OH^(-) " " iv) H_2O_2 + 2OH^(-) - 2e^(-) to O_2 + 2H_2O`

Options

A. i), ii)
B. iii), iv)
C. i), iii)
D. ii), iv)

Answer

D

Explanation

The oxidation states of the species are as follows:
`i) H_2 overset(-1)(O_2) + 2H^(+) + 2e^(-) + 2H_2overset(-2)(O) " " ii) H_2 overset(-1)(O_2) - 2e^(-) to overset(0)(O_2) + 2H^(+)`
`iii) H_2 overset(-1)(O_2) + 2e^(-) to 2overset(-2)OH^(-) " " iv) H_2 overset(-1)(O)H^(-) - 2e^(-) to overset(0)(O_2) + 2H_2 overset(-2)(O)`
In (ii) and (iv) `H_2O_2` acts as a reducing agent as it loses electrons to reduce the other species and itself undergoes oxidation.