I have the mass of the amount of substance, and the molar masses. How do I do this? Is this the same as calculating the number of molecules/ formula units? Also, I know the number of atoms for each element in the compound (It made me calculate that before)

You don't have all of the information for me to answer. Why not type specific question and tell us what you don't understand about it.\

mols = grams/molar mass
# molecules = mols x 6.02E23
# atoms = #molecules x (#atoms/molecule)

To calculate the number of molecules or formula units, given the mass of a substance and its molar mass, you need to use the concept of mole. A mole is a unit used to express the amount of a substance, and it is equal to Avogadro's number (approximately 6.022 x 10^23) particles (atoms, molecules, or formula units).

Here's how you can calculate the number of molecules or formula units:

1. Determine the molar mass of the substance: This is the mass of one mole of the substance and is usually expressed in grams/mole.

2. Use the given mass of the substance to calculate the number of moles: Divide the given mass by the molar mass. The resulting value will be in moles.

Number of moles = Mass of substance (in grams) / Molar mass

3. Use Avogadro's number to convert moles to number of molecules/formula units: Multiply the number of moles by Avogadro's number (6.022 x 10^23) to find the number of molecules or formula units.

Number of molecules/formula units = Number of moles x Avogadro's number

Therefore, calculating the number of molecules or formula units is not the same as calculating the number of atoms for each element in the compound. The number of atoms for each element in the compound tells you the ratio of atoms within a molecule or formula unit, but to calculate the total number of molecules or formula units, you need to consider the molar mass and convert moles to actual count using Avogadro's number.