What is the mass of $33.6 \ dm^3$ of methane gas at $S.T.P.$?

$4.0 \,g$ of $NaOH$ are contained in one decilitre of solution. Its molarity would be ......... $M$.

$10 \ g$ of a piece of marble $(CaCO_3)$ was put into excess of dilute $HCl$ acid. When the reaction was complete,$1120 \ mL$ of $CO_2$ was obtained at $STP$. The percentage of pure $CaCO_3$ in the marble is $............ \%$.

What volume (in $mL$) of $HCl$ solution containing $73 \ g$ per litre is required to completely neutralise sodium hydroxide solution,obtained by allowing $0.46 \ g$ of metallic sodium to act upon water?

To neutralise $20 \, mL$ of $M/10$ sodium hydroxide,the volume of $M/20$ hydrochloric acid required is .............. $mL$

$x \ g$ of methane was burnt completely in the presence of oxygen. The liberated gases were passed into a solution containing $370 \ g$ of $Ca(OH)_2$. The weight of white precipitate obtained was $500 \ g$. What is the value of $x$ (in $g$)? (Given: $C=12, H=1, Ca=40, O=16 \ u$)