A $5.0 \mathrm{~cm}^3$ solution of $\mathrm{H}_2 \mathrm{O}_2$ liberates 1.27 g of iodine from an acidified KI solution. The percentage strength of $\mathrm{H}_2 \mathrm{O}_2$ is close to

What is the four-electron reduced form of $\mathrm{O}_2$ ?

How many electrons are needed to reduce $\mathrm{N}_2$ to $\mathrm{NH}_3 ?$

The equivalent weight of $$\mathrm{Na}_2 \mathrm{S}_2 \mathrm{O}_3(\mathrm{Gram}$$ molecular weight $$=\mathrm{M})$$ in the given reaction is

$$\mathrm{I}_2+2 \mathrm{Na}_2 \mathrm{~S}_2 \mathrm{O}_3=2 \mathrm{NaI}+\mathrm{Na}_2 \mathrm{~S}_4 \mathrm{O}_6$$