How many moles of $H_2O_2$ are required to decolorize $1$ mole of $KMnO_4$ (in $.5$)?

$A$ mixture of $H_2$ and $O_2$ at $1 \, atm$ pressure contains $20 \%$ by weight of $H_2$. Find out the partial pressure of $H_2$ in $atm$.

Equal masses in grams of $H_2$, $N_2$, $Cl_2$, and $O_2$ are enclosed in cylinders separately. If these gases expand isothermally and reversibly by $10 \ dm^3$ at $300 \ K$, the work done by the gas is maximum for:

The mass of sodium acetate $(CH_3COONa)$ required to prepare $250 \ mL$ of $0.35 \ M$ aqueous solution is . . . . . . $g$. (Molar mass of $CH_3COONa$ is $82.02 \ g \ mol^{-1}$)

Molarity of $0.2 \ N \ H_2SO_4$ is

The heat of combustion of ethene $(C_2H_4)$ is $1411 \, kJ$. If a certain amount of ethene is burned to produce $6226 \, kJ$ of heat,what is the volume of $O_2$ (at $S.T.P.$) consumed in the process?