Molar MassMolar mass of potassium chloride (KCl)
The molar mass of potassium chloride, KCl, is 74.55 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 74.55 grams.
74.55 g/mol
39.098 + 35.45 = 74.548 · 2 atoms in the formula · also called muriate of potash
About potassium chloride
Potassium chloride is a white salt used mainly as a potash fertiliser and in low-sodium salt. Like sodium chloride it is built of ions in a one to one ratio.
Other names: muriate of potash.
The working
The formula KCl has 1 potassium atom and 1 chlorine atom, 2 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Potassium (K) | 1 | 39.098 | 39.098 | 52.45% |
| Chlorine (Cl) | 1 | 35.45 | 35.450 | 47.55% |
39.098 + 35.45 = 74.548 g/mol
With the rounded atomic masses used in many school books (K = 39, Cl = 35.5) the answer is 74.5 g/mol. The difference from 74.55 is too small to matter in most school sums.
Percentage composition
By mass, KCl is 52.45% potassium and 47.55% chlorine. The largest share comes from potassium. In a 100 g sample there are 52.4 g of potassium and 47.6 g of chlorine.
Worked examples
Grams to moles. How many moles are in 250 g of KCl? Divide the mass by the molar mass: 250 ÷ 74.55 = 3.354 mol.
Moles to grams. What is the mass of 0.2 mol of KCl? Multiply: 0.2 × 74.55 = 14.91 g.
Counting particles. 250 g contains 3.354 mol × 6.022 × 1023 = 2.020 × 1024 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 74.55 = 7.455 g of KCl in each litre. For 250 mL, weigh 1.864 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 7.455 g |
| 0.5 mol | 37.27 g |
| 1 mol | 74.55 g |
| 2 mol | 149.1 g |
| 5 mol | 372.7 g |
| Mass | Moles |
|---|---|
| 1 g | 0.01341 mol |
| 10 g | 0.1341 mol |
| 100 g | 1.341 mol |
| 1 kg | 13.41 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of KCl?
The molar mass of potassium chloride (KCl) is 74.55 g/mol, or 74.548 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of KCl?
100 ÷ 74.55 = 1.341 mol.
What is the mass of one formula unit of KCl?
Divide the molar mass by the Avogadro constant: 74.55 ÷ 6.022 × 1023 = 1.238 × 10-22 g.
What is the percentage of potassium in KCl?
Potassium makes up 52.45% of the mass of KCl: 1 × 39.098 ÷ 74.548 × 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.