# What is the molar mass of phosphorus?

May 22, 2017

$123.88 \text{g"/"mol}$

#### Explanation:

Step 1. Determine how many of each type of atom there are in the chemical formula ${\text{P}}_{4}$

$\text{ }$In this case, there are 4 phosphorous atoms per molecule

Step 2. Determine the mass of phosphorous from the periodic table

Because the atomic mass of phosphorous is 30.97 amu, we can say the mass is

$m = 4 \times 30.97 = 123.88 \text{g"/"mol}$

This means that 1 mol of ${\text{P}}_{4}$ weighs 123.88 grams.

[NOTE: If you only wanted the molar mass of single atoms of phosphorous, then $m = 30.97 \text{g"/"mol}$; That is a mole of isolated phosphorous atoms would weigh 30.97 grams.]