The Size and Shape of Molecules

Abstract

Some indication of the size of molecules is given by their molecular weight but more precise information can be obtained from measurements of density. For a pure liquid $$ density = \frac{{theweightof1mole}}{{thevolumeof1mole}} = \frac{M}{{{V_m}}}$$ where M is the molecular weight and V m. is the molal volume. If the density can be measured to 4 decimal places, the molal volume can be calculated to 0.1 cm3, and by comparing values of V m. for different compounds, at the same temperature, it is possible to obtain an idea of the size of various groups.1 Some values are listed in Table 3.1.