Molar mass
A mole is a count. The mass you have to weigh out to get that count has a name too — the molar mass.
Molar mass
The molar mass is the mass of one mole of any substance.
This one does have a unit
Relative atomic mass and relative molecular mass carry no units, but the units of molar mass are given as grams per mole (g mol-1) or as kilograms per mole (kg mol-1).
That is the whole difference
The number is identical; only the unit is added. The relative atomic mass of sodium is 23, with no unit. The molar mass of sodium is 23 g mol-1. Whether your answer takes a unit depends on which of the two was asked for.
| Substance | Relative mass | Molar mass |
|---|---|---|
| Sodium (Na) | 23 | 23 g mol-1 |
| Carbon dioxide (CO2) | 44 | 44 g mol-1 |
| Sodium chloride (NaCl) | 58.5 | 58.5 g mol-1 |
| Calcium carbonate (CaCO3) | 100 | 100 g mol-1 |
Only one job is left
You now have everything needed to go from a mass to a number of moles, and from moles to a number of particles. The last section gathers that into a single relationship and practises it.