The mass of one molecule of oxygen is equal to $..... \ kg$.

Elements $X$ and $Y$ form compounds $X_2Y_3$ and $X_3Y_4$ respectively. If $0.2 \ mol$ of $X_2Y_3$ weighs $32.0 \ g$ and $0.4 \ mol$ of $X_3Y_4$ weighs $92.8 \ g$,then the atomic masses of $X$ and $Y$ are respectively:

The density of liquid ethanol is $0.929 \, g \, cm^{-3}$. What is the volume occupied by one mole of ethanol molecules?

The equivalent weight of a divalent metal is $32.7$. The molecular weight of its chloride is .....

The equivalent mass of a divalent metal is $31.82$. What is the mass of a single atom of this metal?

The equivalent mass of an element $X$ is $9$. If the vapor density of its chloride salt is $66.75$,determine the valency of element $X$.