Which of the following statements is true regarding the calculation of moles?

The statement that involves mass and molar mass is valid because calculating moles is fundamentally based on the relationship between the mass of a substance and its molar mass. The formula used for this calculation is:

[ \text{Moles} = \frac{\text{Mass (grams)}}{\text{Molar Mass (grams/mole)}} ]

This means that, to find the number of moles in a given mass of a substance, you need to know both the mass you have and the substance's molar mass. The molar mass is a constant that indicates how much one mole of that substance weighs, and without it, the calculation cannot be completed.

This concept is essential in stoichiometry, where reactions and their predictions rely on understanding the amount of reactants and products in mole quantities. Thus, option B accurately reflects the requirements for calculating moles.