The phrase nacl molar mass refers to the mass of 1 mole of sodium chloride formula units, expressed in g/mol. For an ionic compound like NaCl, the same calculation is often called the formula mass, because the substance is made of formula units rather than discrete molecules.
Goal. Calculate the molar mass (formula mass) of NaCl using periodic-table atomic masses.
Step 1: Count each type of atom in NaCl
The chemical formula NaCl contains:
- 1 sodium atom (Na)
- 1 chlorine atom (Cl)
Step 2: Use atomic masses and compute contributions
Using common periodic-table values: \(M(\mathrm{Na}) \approx 22.99\ \text{g/mol}\), \(M(\mathrm{Cl}) \approx 35.45\ \text{g/mol}\).
| Element | Symbol | Atoms in NaCl | Atomic mass (g/mol) | Contribution (g/mol) |
|---|---|---|---|---|
| Sodium | Na | 1 | 22.99 | \(1 \times 22.99 = 22.99\) |
| Chlorine | Cl | 1 | 35.45 | \(1 \times 35.45 = 35.45\) |
Step 3: Add the contributions to get the NaCl molar mass
\[ M(\mathrm{NaCl}) = (1 \times 22.99) + (1 \times 35.45) = 58.44\ \text{g/mol} \]
Answer. The NaCl molar mass (formula mass) is 58.44 g/mol.
Visualization: Na and Cl contributions to the NaCl molar mass
Common use: converting grams of NaCl to moles
Once the NaCl molar mass is known, mass-to-moles conversion uses: \[ n = \frac{m}{M} \] For a mass \(m\) (in grams) of sodium chloride, \(n = \dfrac{m}{58.44}\) moles.