$25 \ cm^3$ of oxalic acid completely neutralized $0.064 \ g$ of sodium hydroxide. The molarity of the oxalic acid solution is: (in $M$)

$A$ $40 \%$ $HCl$ solution has density $1.2 \ g \ mL^{-1}$. The molarity of the solution is nearly . . . . . . (in $M$)

$A$ solution of $H_2SO_4$ is $31.4 \%$ $H_2SO_4$ by mass and has a density of $1.25 \ g \ mL^{-1}$. The molarity of the $H_2SO_4$ solution is . . . . . . $M$ (nearest integer) [Given molar mass of $H_2SO_4 = 98 \ g \ mol^{-1}$]

When $500 \ mL$ of a gaseous hydrocarbon is burned in excess of $O_2$,it produces $2.5 \ L$ of $CO_2$ and $3.0 \ L$ of water vapor. What is the molecular formula of the hydrocarbon?

The concentration of a $100 \ mL$ solution containing $X \ g$ of $Na_2CO_3$ (molecular weight $= 106$) is $Y \ M$. The values of $X$ and $Y$ are respectively.

$0.01\, M\, KMnO_{4}$ solution was added to $20.0\, mL$ of $0.05\, M$ Mohr's salt solution through a burette. The initial reading of $50\, mL$ burette is zero. The volume of $KMnO_{4}$ solution left in the burette after the end point is $.....\, mL$. (nearest integer)