$A$ gaseous mixture contains $50\%$ Helium and $50\%$ Methane by volume. What is the percentage of Methane by weight in the mixture?

The molarity of $1 \ L$ orthophosphoric acid $(H_3PO_4)$ having $70 \%$ purity by weight (specific gravity $1.54 \ g \ cm^{-3}$) is $ . . . . . . $ $M$.
(Molar mass of $H_3PO_4 = 98 \ g \ mol^{-1}$)

The number of molecules of $CO_2$ liberated by the complete combustion of $0.1 \ mol$ of graphite in air is

$20 \ g$ of hydrogen gas $(H_2)$ is present in a $5 \ L$ vessel. The molar concentration of hydrogen is: (in $M$)

How many grams of $NaCl$ are decomposed by $4.9 \ g$ of $H_2SO_4$ to produce sodium hydrogen sulfate and $1.825 \ g$ of $HCl$? $[Na = 23, Cl = 35.5, S = 32, H = 1, O = 16]$

$2.5 \ cm^{3}$ of $0.2 \ M \ H_{2}SO_{4}$ solution is diluted to $0.5 \ dm^{3}$. Find the normality of the diluted solution. (in $N$)