Final answer:
The claim that formula masses and molar masses are calculated to two significant figures is false. Formula and molar masses are reported with as many significant figures as the measurement precision allows, typically more than two. These masses are critical for determining molecular formulas and the amount of substance present in a given sample.
Step-by-step explanation:
The statement that formula masses (or molecular masses) and molar masses are calculated to two significant figures is false. Formula mass is calculated as the sum of the atomic masses of all the atoms in a compound's empirical formula, each multiplied by its subscript. The molar mass is the mass of one mole of that substance, using the unit grams per mole (g/mol). Both formula mass and molar mass should be reported with as many significant figures as the precision of the measurement allows, which is typically more than two significant figures.
Molecular mass is determined using the molecular formula of a substance and can be experimentally measured through techniques such as mass spectrometry. The molecular mass is then compared to the empirical formula mass to determine the number of empirical formula units per molecule, designated as n. This is a key step in deriving a compound's molecular formula.
Derivation of molecular formulas requires both empirical formula and molecular or molar mass knowledge. The empirical formula mass is the sum of the average atomic masses of all the elements represented in an empirical formula. This is essential to determine the number of atoms present in a single molecule of a covalent compound.