What is the relationship between the mass of a substance and the number of moles?

The correct answer highlights a fundamental relationship in chemistry that connects mass to the number of moles of a substance through the concept of molar mass. The equation mass = moles × molar mass effectively shows that the mass of a substance is directly proportional to the number of moles when the molar mass remains constant. This means that if you increase the number of moles of a substance, its mass also increases proportionally, assuming the molar mass does not change.

The direct relationship is critical because it allows chemists to convert between mass and the number of moles using the molar mass, which is a specific value for each substance indicating how many grams correspond to one mole. This relationship is fundamental in stoichiometric calculations, enabling the prediction of amounts of reactants or products in chemical reactions based on mole ratios.

Understanding this relationship is vital in chemistry, as it forms the basis for various calculations involving chemical substances, showing how mass measurement directly relates to the number of moles present in a sample.