Chemistry
Moles from a weighed mass
The bridge from the balance to the mole. Molar mass is the sum of atomic masses, in grams per mole.
The Formula
n = m / Mr
The bridge from the balance to the mole. Molar mass is the sum of atomic masses, in grams per mole.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| m | Mass of solute | grams | What the balance reads, before any chemistry happens. |
| Mr | Molar mass | g/mol | Grams per mole. 40 g/mol turns 20 g into 0.5 mol. |
What Each Symbol Means
mgrams
Mass of solute
What the balance reads, before any chemistry happens.
Mrg/mol
Molar mass
Grams per mole. 40 g/mol turns 20 g into 0.5 mol.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to calculate molarity page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Calculate Molarity, filed under Science. Every number the guide produces comes from substituting into this one line.