# What percentage does oxygen make up in the compound MgSO_4?

Mar 12, 2017

Oxygen makes up 53.16%

#### Explanation:

In order to compute the mass percent of oxygen in $M g S {O}_{4}$ we're going to need two things:

$\textcolor{p u r p \le}{\text{1: The formula mass of the entire compound}}$
$\textcolor{p u r p \le}{\text{2: The atomic mass of oxygen}}$

The formula mass of $M g S {O}_{4}$ is 120.38 $\frac{g}{m o l}$
$1 \left(24.31 \frac{g}{m o l}\right) + 1 \left(32.07 \frac{g}{\text{mol") +4(16.00 g/"mol}}\right)$ $= 120.38 \frac{g}{m o l}$

The atomic mass of the oxygen atom is $16.00 \frac{g}{m o l}$

Now, we have to use the following equation: The numerator represents the mass of the desired atom, which is O in our case, and the denominator represents the mass of the entire compound. You just divide the two and multiply by 100 to obtain the percent composition:

"Mass of O"/("Molar Mass of "MgSO_4") xx100%

"(4)16.00 g/mol"/"120.38g/mol"xx100% = 53.16%

I multiplied the atomic mass of oxygen by 4 because you have to account for all of the oxygen atoms in the formula.