Final answer:
To calculate the number of moles of a known mass of a substance, one must use the molar mass as a conversion factor. The equation n = m/M, where n is the number of moles, m is the mass, and M is the molar mass, can be used to convert mass to moles or moles to mass.
Step-by-step explanation:
When we know the mass and chemical composition of a substance, we can calculate the number of moles of the sample. The process involves using the molar mass as a conversion factor. The equation to calculate moles from molar mass is: n = m/M, where n is the number of moles, m is the mass, and M is the molar mass. Using this formula, we can easily convert mass to moles and vice versa.
For instance, if we are given the mass of a substance and need to calculate the number of moles, we simply divide the mass of the substance by its molar mass. Conversely, if we have the number of moles of a substance and want to find the mass, we multiply the number of moles by the molar mass.
If the chemical formula of a substance is unknown, we can still apply these principles to derive the chemical formulas of unknown substances from experimental mass measurements.