$50 \mathrm{mL}$ of ${\mathrm{H}}_2{\mathrm{O}}_2$ was treated with excess of $\mathrm{KI}$ in the presence of dilute sulphuric acid. ${\mathrm{I}}_2$ so liberated was titrated with $20 \mathrm{mL}$ of $0.1 \mathrm{N}$ hypo solution. Calculate the strength of ${\mathrm{H}}_2{\mathrm{O}}_2$ in grams per litre.

A zinc rod weighing $25.00 \mathrm{g}$ was kept in $100 \mathrm{mL}$ of $1 \mathrm{M} {\mathrm{CuSO}}_4$ solution. After a certain time, molarity of ${\mathrm{Cu}}^{2+}$ in solution was $0.8 \mathrm{M}$. What was the molarity of the sulphate ion $\left({\mathrm{SO}}_4^{2-}\right)$? What was the weight of the zinc rod after cleaning?

Give the answer upto three places of decimal.

A zinc rod weighing $25.00 \mathrm{g}$ was kept in $100 \mathrm{mL}$ of $1 \mathrm{M} {\mathrm{CuSO}}_4$ solution. After a certain time, molarity of ${\mathrm{Cu}}^{2+}$ in solution was $0.8 \mathrm{M}$.

If the above experiment was done with a copper rod of weight $25 \mathrm{g}$ and $50$ $\mathrm{mL}$ of $2 \mathrm{M}$ zinc sulphate $\left({\mathrm{ZnSO}}_4\right)$ solution, what would be the molarity of ${\mathrm{Zn}}^{2+}$ at the end of the same interval? 

A sample of hydrazine sulphate $\left({\mathrm{N}}_2{\mathrm{H}}_4{\mathrm{SO}}_4\right)$  was dissolved in $100 \mathrm{mL}$ of water. $10 \mathrm{mL}$ of this solution was reacted with excess of ferric chloride solution and warmed to complete the reaction. Ferrous ion formed was estimated and it required $20 \mathrm{mL}$ of $\mathrm{M}/50$ potassium permanganate solution. Estimate the amount of hydrazine sulphate in one litre of the solution. Reactions:

$4{\mathrm{Fe}}^{+++}+{\mathrm{N}}_2{\mathrm{H}}_4\to {\mathrm{N}}_2+4{\mathrm{Fe}}^{++}+4{\mathrm{H}}^{+}$

${\mathrm{MnO}}_4^{-}+5{\mathrm{Fe}}^{++}+8{\mathrm{H}}^{+}\to {\mathrm{Mn}}^{++}+5{\mathrm{Fe}}^{+++}+4{\mathrm{H}}_2\mathrm{O}$