If the formula is a molecular formula, the mass associated with it is called molecular mass or molecular weight. As an exercise, work out the following problem. What is the molecular weight of caffeine, \(\ce{C8H10N4O2}\)? The diagram shown here is a model of the caffeine molecule. Conclusion: Molar mass is the smallest unit of a compound with one-twelfth of the mass of one carbon – 12 atoms. Gram molecular mass is the mass of one mole of a molecular substance in grams. It is the sum of all the molecular weight of each atom present in the molecule multiplied by its subscript. The unit used to measure is grams per mole. 6 O molar mass: 6 × 16.00 g =. 96.00 g. Total: 584.73 g. The molar mass of bilirubin is 584.73 g. Using the relationship. 1 mol bilirubin = 584.73 g bilirubin. we can construct the appropriate conversion factor for determining how many grams there are in 0.00655 mol. Molecular weight and molar mass are not exactly the same, but they are closely related terms. Molecular weight refers to the average mass of the molecule. On other hand, the molar mass is the mass of one mole of a substance. Calculate the percent by mass of each element by dividing the mass of that element in 1 mole of the compound by the molar mass of the compound and multiplying by 100% 100 %. Think about your result. The percentages add up to 100% 100 %. Percent composition can also be used to determine the mass of a certain element that is contained in any mass The quantity molar mass (quantity symbol: M M) for a pure sample is defined as. M = m/n M = m / n. where m m is mass and n n is amount of substance. The dimension of the molar mass is. dim M = M N−1 dim M = M N − 1. The coherent SI unit for molar mass is ‘kilogram per mole’ (unit symbol: kg/mol k g / m o l ). 1 Answer. Vapour density (ρv) ( ρ v) of a gas is not the absolute density, such as mass density m/V m / V or number density N/V N / V. It is in fact relative density, compared to the density of some other, reference gas at the same temperature and pressure: ρv = ρ ρref. (1) (1) ρ v = ρ ρ ref. Molar mass can be measured by a number of experimental methods, many of which will be introduced in later chapters of this text. Molecular formulas are derived by comparing the compound’s molecular or molar mass to its empirical formula mass. As the name suggests, an empirical formula mass is the sum of the average atomic masses of all the zYQP.