Question

A mixture contains 4.00 x 10^23 molecules of PCl3. How many grams of PCl3 does this sample contain?

Answer 1

91.2 g of PCl3.

Step-by-step explanation:

What is given?

molecules of PCl3 = 4.00 x 10²³ molecules.

molar mass of PCl3 = 137.3 g/mol (you can calculate this using the periodic table).

Avogadro's number = 6.022 x 10²³ molecules/mol.

Step-by-step solution:

First, we have to convert from molecules to moles using Avogadro's number, which says that there are 6.022 x 10²³ molecules in 1 mol. The conversion will look like this:

`4.00\cdot10²³\text{ }molecules\text{ PCl}_3\cdot\frac{1\text{ mol}}{6.022\cdot10²³}=0.664\text{ moles PCl}_3.`

And the final step is to convert from 0.664 moles of PCl3 to grams using its molar mass which is given at the beginning (137.3 g/mol):

`0.664\text{ moles PCl}_3\cdot\frac{137.3\text{ g PCl}_3}{1\text{ mol PCl}_3}=91.2\text{ g PCl}_3.`

The answer is that we have 91.2 g of PCl3 in 4.00 x 10²³ molecules of PCl3.