Molar mass is the mass of one mole of a chemical element or chemical compound.

The molecular mass of a substance, also called molecular weight, is the mass of one molecule of that substance.

Abbreviated explanation

Molar mass is sometimes confused with the related but distinct molecular mass.

The molar mass is generally computed from isotopically weighted averages, whereas the molecular mass is the mass of a single molecule consisting of well-defined isotopes.

It is common, even amongst professional chemists, to use the terms interchangeably since for most common applications the difference is insignificant. This can, however, on occasion lead to substantive confusion. Due to this common practice some areas of chemistry have developed their own more specific terms such as monoisotopic mass and average mass.

–Extracted From Wiki

Molar mass is sometimes confused with the related but distinct molecular mass. This is largely due to that when the molar mass and molecular mass are expressed in g/mol and u respectively they will almost always have similar but not identical numerical values. The molar mass is generally computed from isotopically weighted averages, whereas the molecular mass is the mass of a single molecule consisting of well-defined isotopes. The isotopically weighted averages used to compute molar masses are those found in most versions of the periodic table and are numbers recommended by IUPAC. They represent the most likely weights of substances found in the laboratory. The averaging takes into account the natural abundance of, usually heavier, isotopes as well as the variation in their natural abundance in different places on earth. Additionally the confidence, or number of significant figures after the decimal, is different. The significant figures in the standard atomic weights and thus the computed molar masses are often limited by the natural variations in the isotopic distributions and not necessarily by our ability to measure accurately. The confidence in the isotopic masses and resulting molecular masses are only limited by the accuracy of measurement of the invariable isotopic masses.

It is common, even amongst professional chemists, to use the terms interchangeably since for most common applications the difference is insignificant. This can, however, on occasion lead to substantive confusion. Due to this common practice some areas of chemistry have developed their own more specific terms such as monoisotopic mass and average mass. Due to these subtle differences and the inherent nature of the molar mass it is always more correct, accurate and consistent to use molar mass in any bulk stoichiometric calculations.

Hope this helps.

Molecular Mass versus Molar Mass

The molar mass of a substance is the mass of 1 mol (the SI unit for the basis SI quantity amount of substance, having the symbol n). This has a numerical value which is approximately the molecular mass multiplied by Avogadro’s constant 6.022*1023, and the SI unit kg/mol, usually also found as stated in g/mol .

Approximate Conversion Factor of molecular mass to molar mass

molar mass = molecular mass * (6.022*1023)

Example:

The atomic mass of hydrogen is 1.00794 u and that of oxygen is 15.9994 u;

therefore, the molecular mass of water with formula H2O is (2 × 1.00794 u) + 15.9994 u = 18.01528 u. Therefore, one mole of water has a mass of 18.01528 grams. However, the exact mass of hydrogen-1 (the most common isotope) is 1.00783, and the exact mass of oxygen-16 (the most common isotope) is 15.9949, so the mass of the most common single molecule of water is 18.01056 u. This is a difference of 0.00472 u or 0.03%. Although this difference is trivial in bulk calculations, it can result in complete failure in situations where the behavior of individual molecules matters, such as in particle physics (where the mixture of isotopes does not act as an average).

They are essentially the same thing, though the molar mass is in Atomic Mass Units (1 AMU = the mass of one proton) while the molar mass is in grams. However, 1 mole of AMU’s = 1 gram, so essentially they are the same thing.

molecular mass is the weight of the molecule and molar mass is the weight of how many molecules fits in a mole. one mole is 6.022 x 10 (23) molecules.

molar mass is how many moles the substance is comprised of. molecular mass is the mass of the molecule(s) of that substance. a mole is 6.03 x 10^23 molecules.