Question

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

Answer 1

Oxygen makes up `53.16%`

Explanation:

In order to compute the mass percent of oxygen in `MgSO_4` we're going to need two things:

`color(purple)"1: The formula mass of the entire compound"`
`color(purple)"2: The atomic mass of oxygen"`

The formula mass of `MgSO_4` is 120.38 `g/(mol)`
`1(24.31g/(mol)) + 1(32.07g/"mol") +4(16.00 g/"mol")` `= 120.38g/(mol)`

The atomic mass of the oxygen atom is `16.00 g/(mol)`

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.