Chlorine trifluoride is a colorless, reactive gas used in nuclear fuel reprocessing. How many molecules are there in a 5.88-mg sample of chlorine trifluoride?

Image from: Ebbing, Darrell D., and Steven D. Gammon. General Chemistry. Australia: Brooks/Cole Cengage Learning, 2010.

#### Solution:

### Let us first calculate the molar mass of chlorine trifluoride.

### Molar mass of \text{ClF}_3= 35.453 amu + (3\times 18.998) amu = 92.45 amu = 92.45 g/mol

### We will now use Avogadro’s number to calculate how many molecules there are in the 5.88 mg sample.

### 5.88 \text{mg}\times \frac{1 \text{g}}{1000 \text{mg}}\times \frac{6.022\times 10^{23}\text{molecules}}{92.45\text{g}\, \text{ClF}_3}=3.830\times 10^{19}\text{molecules}

###### This question can be found in General Chemistry, 9th edition, chapter 3, question 3.48