Final answer:
True, the number of moles of a substance with a known molar mass can be calculated from the mass of the sample using the equation n = m/M.
Step-by-step explanation:
For a substance with a known molar mass, the statement "the number of moles of a sample can be calculated from the mass of the sample" is True.
This is because the number of moles (n) of a substance is calculated by dividing the mass (m) of the substance by its molar mass (M), as shown by the equation n = m/M. It is one of the fundamental principles in chemistry used to relate the mass of a substance to the number of its constituent particles, be they atoms, molecules, or formula units.