Molar MassMolar mass of sodium hypochlorite (NaClO)
The molar mass of sodium hypochlorite, NaClO, is 74.44 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 74.44 grams.
74.44 g/mol
22.990 + 35.45 + 15.999 = 74.439 · 3 atoms in the formula · also called the active part of liquid bleach
About sodium hypochlorite
Sodium hypochlorite is the active ingredient of household liquid bleach, which is a dilute solution of it in water. It kills germs and removes colour by oxidation.
Other names: the active part of liquid bleach.
The working
The formula NaClO has 1 sodium atom, 1 chlorine atom and 1 oxygen atom, 3 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Sodium (Na) | 1 | 22.990 | 22.990 | 30.88% |
| Chlorine (Cl) | 1 | 35.45 | 35.450 | 47.62% |
| Oxygen (O) | 1 | 15.999 | 15.999 | 21.49% |
22.990 + 35.45 + 15.999 = 74.439 g/mol
With the rounded atomic masses used in many school books (Na = 23, Cl = 35.5, O = 16) the answer is 74.5 g/mol. The difference from 74.44 is too small to matter in most school sums.
Percentage composition
By mass, NaClO is 30.88% sodium, 47.62% chlorine and 21.49% oxygen. The largest share comes from chlorine. In a 100 g sample there are 30.9 g of sodium, 47.6 g of chlorine and 21.5 g of oxygen.
Worked examples
Grams to moles. How many moles are in 40 g of NaClO? Divide the mass by the molar mass: 40 ÷ 74.44 = 0.5374 mol.
Moles to grams. What is the mass of 3 mol of NaClO? Multiply: 3 × 74.44 = 223.3 g.
Counting particles. 40 g contains 0.5374 mol × 6.022 × 1023 = 3.236 × 1023 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 74.44 = 7.444 g of NaClO in each litre. For 250 mL, weigh 1.861 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 7.444 g |
| 0.5 mol | 37.22 g |
| 1 mol | 74.44 g |
| 2 mol | 148.9 g |
| 5 mol | 372.2 g |
| Mass | Moles |
|---|---|
| 1 g | 0.01343 mol |
| 10 g | 0.1343 mol |
| 100 g | 1.343 mol |
| 1 kg | 13.43 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of NaClO?
The molar mass of sodium hypochlorite (NaClO) is 74.44 g/mol, or 74.439 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of NaClO?
100 ÷ 74.44 = 1.343 mol.
What is the mass of one formula unit of NaClO?
Divide the molar mass by the Avogadro constant: 74.44 ÷ 6.022 × 1023 = 1.236 × 10-22 g.
What is the percentage of chlorine in NaClO?
Chlorine makes up 47.62% of the mass of NaClO: 1 × 35.45 ÷ 74.439 × 100.
Which values? This site uses the abridged standard atomic weights published by IUPAC (CIAAW), read on 12 November 2026. Your textbook or question paper may round them differently, for example H = 1 and O = 16, so its answer can differ slightly. In an exam, use the values the paper gives.