Molar MassMolar mass of copper(II) chloride (CuCl2)
The molar mass of copper(II) chloride, CuCl2, is 134.45 g/mol. One mole of it, which is 6.022 × 1023 formula units, has a mass of 134.45 grams.
134.45 g/mol
63.546 + 2 × 35.45 = 134.446 · 3 atoms in the formula · also called cupric chloride
About copper(II) chloride
Copper(II) chloride is a brown solid when anhydrous and blue-green as the dihydrate. It gives a blue-green colour in a flame test.
Other names: cupric chloride.
The working
The formula CuCl2 has 1 copper atom and 2 chlorine atoms, 3 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Copper (Cu) | 1 | 63.546 | 63.546 | 47.27% |
| Chlorine (Cl) | 2 | 35.45 | 70.900 | 52.73% |
63.546 + 2 × 35.45 = 134.446 g/mol
With the rounded atomic masses used in many school books (Cu = 63.5, Cl = 35.5) the answer is 134.5 g/mol. The difference from 134.45 is too small to matter in most school sums.
Percentage composition
By mass, CuCl2 is 47.27% copper and 52.73% chlorine. The largest share comes from chlorine. In a 100 g sample there are 47.3 g of copper and 52.7 g of chlorine.
Worked examples
Grams to moles. How many moles are in 250 g of CuCl2? Divide the mass by the molar mass: 250 ÷ 134.45 = 1.859 mol.
Moles to grams. What is the mass of 0.2 mol of CuCl2? Multiply: 0.2 × 134.45 = 26.89 g.
Counting particles. 250 g contains 1.859 mol × 6.022 × 1023 = 1.120 × 1024 formula units.
Making a solution. A 0.1 mol/L solution contains 0.1 × 134.45 = 13.44 g of CuCl2 in each litre. For 250 mL, weigh 3.361 g and make it up to the mark with water.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 13.44 g |
| 0.5 mol | 67.22 g |
| 1 mol | 134.4 g |
| 2 mol | 268.9 g |
| 5 mol | 672.2 g |
| Mass | Moles |
|---|---|
| 1 g | 0.007438 mol |
| 10 g | 0.07438 mol |
| 100 g | 0.7438 mol |
| 1 kg | 7.438 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of CuCl2?
The molar mass of copper(II) chloride (CuCl2) is 134.45 g/mol, or 134.446 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of CuCl2?
100 ÷ 134.45 = 0.7438 mol.
What is the mass of one formula unit of CuCl2?
Divide the molar mass by the Avogadro constant: 134.45 ÷ 6.022 × 1023 = 2.233 × 10-22 g.
What is the percentage of chlorine in CuCl2?
Chlorine makes up 52.73% of the mass of CuCl2: 2 × 35.45 ÷ 134.446 × 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.