The density of $2 \ M$ aqueous solution of $NaOH$ is $1.28 \ g \ cm^{-3}.$ The molality of the solution is $... \ m$ [Given that molecular mass of $NaOH = 40 \ g \ mol^{-1}$]

$A$ pre-weighed vessel is filled with $O_2$ and weighed at $STP$. It is then evacuated and filled with $SO_2$ gas at the same temperature and pressure,and weighed again. The weight of $O_2$ will be:

$A$ metal chloride contains $55.0 \%$ of chlorine by weight. $100 \ mL$ of vapours of the metal chloride at $STP$ weigh $0.57 \ g$. The molecular formula of the metal chloride is $...$. (Given: Atomic mass of chlorine is $35.5 \ u$)

At $STP$,'$x$' $g$ of a metal hydrogen carbonate $(MHCO_3)$ (molar mass $84 \ g \ mol^{-1}$) on heating gives $CO_2$,which can completely react with $0.2 \ mol$ of $MOH$ (molar mass $40 \ g \ mol^{-1}$) to give $MHCO_3$. The value of '$x$' is

To neutralize $10 \, mL$ of $M/5$ $NaOH$,the volume of $M/20$ $HCl$ required is......$mL$.

The chloride of a metal is $MCl_2$. The formula of its phosphate will be: