How do you calculate the mass percentage of different constituent elements in urea?

Sep 8, 2016

$\text{% element}$ $=$ "Mass of element"/"Molar mass of element"xx100%

Explanation:

For urea, $C O {\left(N {H}_{2}\right)}_{2}$, the molar mass is $60.06 \cdot g \cdot m o {l}^{-} 1$.

And thus $\text{% nitrogen}$

$=$ (2xx14.01*g*mol^-1)/(60.06*g*mol^-1)xx100%=46.6%

$\text{% oxygen}$ $=$ ??

$\text{% hydrogen}$ $=$ ??

You will know if you are right if all the percentages add up to 100%. Why should this be so?