The mass of nitrogen that combines with $40 \ g$ of oxygen in $N_2O_5$ is ............ $g$.

$A$ solution of $CaCl_2$ is $0.5 \, mol/L$. The number of moles of chloride ions in $500 \, mL$ of this solution will be:

How many grams of $60\% \, H_2SO_4$ are required for the complete reaction of $100 \, g \, CaCO_3$?

How many molecules of carbon dioxide are formed when $0.6 \ g$ carbon is burnt in air?

If the density of methanol is $0.793 \ kg \ L^{-1}$,what volume is needed to prepare $2.5 \ L$ of a $0.25 \ M$ solution (in $mL$)?

The decomposition of $H_2O_2$ produces $O_2$. If at a certain time,$48 \ g$ of $O_2$ is produced in $1 \ minute$,then the rate of formation of water at that time will be .......... $mol \ min^{-1}$.