a. When `H_(2)O_(2)` is added to blood, rapid evolution of a gas occures. Why ?
b. Hydrogen peroxide acts both as an oxidising and as a reducing agent in alkaline solution towards certain first row transition metal ions. Illustration both these properties of `H_(2)O_(2)` using chemical equations.

Explanation

a. The enzyme present in the blood catalyst the oxidation
of `H_(2)O_(2)` and hence rapid evolution of `O_(2)` takes place.
`2H_(2)O_(2)overset("Enzyme")underset(("in blood"))to2H_(2)O+O_(2) uarr`
(b). As oxidising agent in basic medium: Chromium hydroxide is oxidized by `H_(2)O_(2)` in presence of `Na OH` into sodium chromate.
`{:(" "[H_(2)O_(2)toH_(2)O+[O]]xx3),(2Cr+(OH)_(3)+NaOH+3[O]to2Na_(2)CrO_(4)+5H_(2)O),(ulbar(2Cr(OH)_(3)+4NaOH+3H_(2)O_(2)to2Na_(2)CrO_(4)+8H_(2)O)):}`