Question

How many molecules are in 71.9 grams of Cl2?

Answer 1

How many molecules are in 71.9 grams of Cl2?

**Solution:**

One mole of any substance contains $6,02 \cdot 10^{23}$ molecules.

The molar mass of $\mathrm{Cl}_2$ is $\mathrm{M}(\mathrm{Cl}_2) = 35.45 \cdot 2 = 70.9\ \mathrm{g/mol}$.

So that, $70.9\ \mathrm{g}$ of $\mathrm{Cl}_2$ contains $6,02 \cdot 10^{23}$ molecules, and

$71.9\ \mathrm{g}$ of $\mathrm{Cl}_2$ contains $n$ molecules.

So, $n(\mathrm{Cl}_2) = \frac{71.9 \cdot 6.02 \cdot 10^{23}}{70.9} = 6.105 \cdot 10^{23}$ molecules.

**Answer:** The number of molecules in 71.9 grams of $\mathrm{Cl}_2$ there are $6.105 \cdot 10^{23}$.