Final answer:
The molar mass of an unknown compound is found by calculating the empirical formula molar mass (EFM), dividing the compound's molar mass by the EFM to get a whole number, and then multiplying the subscripts in the empirical formula by this whole number to get the molecular formula.
Step-by-step explanation:
To find the molar mass of an unknown compound, you need to perform several steps. First, determine the empirical formula molar mass (EFM), which is the sum of the masses of all the atoms in the empirical formula as given by the periodic table. Then, you divide the compound's molar mass by the EFM to get a whole number, which indicates the ratio between the molecular formula and the empirical formula.
Next, you multiply the subscripts in the empirical formula by this whole number to obtain the molecular formula. If you already know the number of moles and the molar mass is given, you multiply them to get the mass of the substance. This is especially useful in scenarios where a chemical reaction is involved and you start with a known mass of one substance and need to find the corresponding mass of another substance using balanced chemical equations.
For example, if you determine the EFM to be 30 g/mol and the molar mass of the compound is 60 g/mol, dividing 60 by 30 gives you 2. This means that the molecular formula contains twice as many atoms as the empirical formula, and you would multiply all the subscripts in the empirical formula by 2 to find the molecular formula.