Final answer:
To determine a compound's molecular formula, one must know its empirical formula and its molecular mass or molar mass. Empirical formula gives the simplest ratio of elements, while molecular mass is needed to convert it to the molecular formula.
Step-by-step explanation:
Determining the Molecular Formula
To determine the molecular formula of a compound, two key pieces of information are required: the empirical formula of the compound and its molecular mass or molar mass. The empirical formula represents the simplest whole-number ratio of the elements in the compound. Meanwhile, the molecular mass is the sum of the mass of all the atoms in the molecule, and molar mass is the mass of one mole of that compound.
To illustrate, consider a covalent compound like glucose with the molecular formula C6H12O6. The molecular formula tells us that a single molecule of glucose is formed from six carbon atoms (C), twelve hydrogen atoms (H), and six oxygen atoms (O). To determine this molecular formula from the empirical formula (which could be CH2O), it is essential to know the molar mass of glucose and compare it to the mass of the empirical formula to find the multiplier needed to convert the empirical formula into the molecular formula.