How can you calculate the number of moles of a substance?

The correct method to calculate the number of moles of a substance is through the relationship between mass and molar mass, as expressed in the formula: Moles = mass (g) / molar mass (g/mol). This formula is derived from the definition of a mole, which is a quantity that links the mass of a substance to the number of particles (atoms, molecules, ions) it contains.

Using this formula, one can determine how many moles are present in a given mass of a substance by simply dividing the mass (in grams) by the molar mass (in grams per mole). The molar mass is a unique property that varies between substances and is usually found on the periodic table or specified for compounds.

In contrast, other options misrepresent the relationship between mass, volume, and moles. For instance, dividing mass by volume would yield a measure of density but not the number of moles. Similarly, multiplying volume by molar mass does not conform to the definitions and relationships of the physical quantities involved. Lastly, multiplying mass by density would not yield moles but rather a measure of volume, further demonstrating that only the correct formula involving mass and molar mass accurately provides the number of moles.