How many molecules of ammonia gas are present in $67.2 \ dm^3$,measured at $S.T.P.$?

What is the number of water molecules present in $1 \ mL$ of water?

Explain the terms: Avogadro constant,molar volume of $1$ mole of gas,and $STP$.

Natural abundances of $^{12}C$ and $^{13}C$ isotopes of carbon are $99\,\%$ and $1\,\%$,respectively. Assuming they only contribute to the molecular weight of $C_2F_4$,the percentage of $C_2F_4$ having a molecular mass of $101$ is $.....$

The number of molecules present in $1 \ cm^{3}$ of water is

Weight of $112 \, mL$ of oxygen at $NTP$ on liquefaction would be .............. $g$.