How do you calculate the number of moles of an element given the mass?

To find the number of moles of an element, you can use the relationship defined by the formula: the number of moles is equal to the mass of the substance divided by its molar mass. This is derived from the definition of a mole, which is the amount of substance that contains as many entities (such as atoms or molecules) as there are in 12 grams of carbon-12.

In mathematical terms, this is expressed as:

n(Moles) = M(Mass) / mm(Molar mass)

Here, "M" represents the mass of the element (in grams), and "mm" denotes the molar mass (in grams per mole). By dividing the mass by the molar mass, you effectively convert grams of the substance into moles, thus allowing you to quantify the amount of substance in terms of moles, facilitating comparisons and calculations in chemical reactions.

The other options do not properly reflect the correct relationship for calculating moles. For instance, simply multiplying mass by molar mass or adding them does not yield the number of moles, as those operations do not follow the stoichiometric principles defined in chemistry.