Question

Maleic acid is an organic compound composed of 41.39% C, 3.47% H, and the rest oxygen. If0.129 mole of maleic acid has a mass of 15.0 g, what are the empirical and molecular formulas of maleic acid?

Short answer

The empirical formula and molecular formula of maleic acid are CHO and$C_4{H}_4{O}_4$.

Step-by-step solution

Finding moles and empirical formula

The mass of carbon in 100 g of maleic acid is 41.39 g. Mass of hydrogen is 3.47 g. Mass of oxygen is $100-\left(41.39+3.47\right)=55.14\mathrm{g}$To find the moles of each compound,

$\begin{array}{rcl}C& =& \frac{41.39}{12.01}\\ & =& 3.446\\ O& =& \frac{55.14}{15.999}\\ & =& 3.446\\ H& =& \frac{3.47}{1.0079}\\ & =& 3.443\end{array}$

The moles are same here. The empirical formula could be CHO.

Finding empirical formula mass

The empirical formula mass can be$12.01+1.0079+15.999=29.0169\raisebox{1ex}{$\mathrm{g}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{mol}$}\right.$

Finding molar mass and molecular formula

The molar mass of maleic acid can be denoted as,

$\begin{array}{rcl}& =& \frac{\mathrm{Mass}}{\mathrm{Mole}\mathrm{number}}\\ & =& \frac{15\mathrm{g}}{0.129{\displaystyle \raisebox{1ex}{$\mathrm{g}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{mol}$}\right.}}\\ & =& 116.27\raisebox{1ex}{$\mathrm{g}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{mol}$}\right.\\ \mathrm{n}& =& \frac{\mathrm{Molar}\mathrm{mass}}{\mathrm{Empirical}\mathrm{mass}}\\ & =& \frac{116.27}{29.0169}\\ & =& {\mathrm{C}}_4{\mathrm{H}}_4{\mathrm{O}}_4\end{array}$