How many moles of $H_2O_2$ are required for the decolorization of $1$ mole of $KMnO_4$?

What amount of conc. $H_2SO_4$ solution should be used to prepare $500 \ mL$ of $0.5 \ M \ H_2SO_4$ (in $g$)? (The concentration of $H_2SO_4$ solution being used is $90\%$ and molecular mass of $H_2SO_4 = 98.079 \ g \ mol^{-1}$)

$15 \ mL$ of $0.2 \ N$ alkali is required to complete neutralization of $30 \ mL$ acid solution. The concentration of the acid solution is ..... $N$.

$A$ sample of a metal oxide has the formula $M_{0.83}O_{1.00}$. The metal $M$ can exist in two oxidation states,$+2$ and $+3$. In the sample of $M_{0.83}O_{1.00}$,the percentage of metal ions existing in the $+2$ oxidation state is $.........\%$ (nearest integer).

The reduction of boron trichloride $(BCl_3)$ by hydrogen yields elemental boron (atomic mass $10.8 \ g/mol$). If $21.6 \ g$ of boron is produced,what is the volume of hydrogen gas required at $273 \ K$ and $1 \ atm$ pressure (in $L$)?

The mass percentage composition of dry air at sea level is approximately $N_2: 63 \%$, $O_2: 16 \%$, $Kr: 21 \%$. If the total pressure is $p \ atm$, calculate the partial pressure of each component respectively. (Molecular weights: $N_2 = 28, O_2 = 32, Kr = 84$)