# How do you calculate the percent composition by mass of O in picric acid (C_6H_3N_3O_7)?

Dec 29, 2016

Since one mole of picric acid contains seven moles of oxygen atoms, this accounts for 48.9% of the total mass.

#### Explanation:

Start by determining the molar mass of picric acid = 229 g

Next, noting that the molecule contains seven oxygen atoms, we can reason that one mole of picric acid must contain seven moles of oxygen atoms.

Find the mass of 7 moles of $O$ = 112 g.

Now, since 112 g out of the total mass of 229 g of picric acid is due to oxygen, express this as a percentage:

112g/(229g) xx 100 = 48.9%

That's it! (You can of course, repeat this process for as many elements as you need in the formula.)

Dec 29, 2016

Approx. 49% by mass......................

#### Explanation:

%O $=$ $\text{Mass of oxygen"/"Molecular mass of picric acid}$

=(7xx15.999*g*mol^-1)/(229.10*g*mol^-1)xx100% =??%