# How can I calculate the percent composition of C4H4O?

##### 1 Answer
Jun 4, 2014

To find the percent composition of C₄H₄O, you divide the total mass of each atom by the molecular mass and multiply by 100 %.

% by mass = $\text{mass of component"/"total mass}$ × 100 %

Mass of 4 C atoms = 4 C atoms × $\left(12.01 \text{u")/(1"C atom}\right)$ = 48.04 u.

Mass of 4 H atoms = 4 H atoms × $\left(1.008 \text{u")/(1"H atom}\right)$ = 4.032 u

Mass of 1 O atom = 1 O atom × $\left(16.00 \text{u")/(1"O atom}\right)$ = 16.00 u

Mass of 1 C₄H₄O molecule = (48.04 + 4.032 + 16.00) u = 68.07 u

% of C = $\text{mass of C"/"total mass}$ × 100 % = $\left(48.04 \text{u")/(68.07"u}\right)$ × 100 % = 70.57 %

% of H = $\text{mass of H"/"total mass}$ × 100 % = $\left(4.032 \text{u")/(68.07"u}\right)$ × 100 % = 5.923 %

% of O = $\text{mass of O"/"total mass}$ × 100 % = $\left(16.00 \text{u")/(68.07"u}\right)$ × 100 % = 23.50 %