$A$ mixture of $1.65 \times 10^{21}$ molecules of $X$ and $1.85 \times 10^{21}$ molecules of $Y$ weighs $0.688 \ g$. If the molecular mass of $Y$ is $187 \ g/mol$,what is the molecular mass of $X$?

The oxide of a metal contains $40 \%$ of oxygen. The valency of the metal is $2$. What is the atomic weight of the metal?

The specific heat of a solid element is $0.1 \text{ cal/g } ^\circ C$ and its equivalent weight is $31.8$. What is its atomic weight?

In Victor Mayer’s method,$0.2 \ g$ of an organic substance displaced $56 \ mL$ of air at $STP$. The molecular weight of the compound is:

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 average molar mass of chlorine is $35.5 \ g \ mol^{-1}$. The ratio of $^{35}Cl$ to $^{37}Cl$ in naturally occurring chlorine is close to : (in $:1$)