# How to determine the molecular formula of a compound given its molecular mass and mass percentage contribution of the involved elements?

Hydralazine is a drug used to treat heart disease. It is $59.99\%$ carbon, $5.03\%$ hydrogen, and $34.98\%$ nitrogen and has a molecular mass of $160.178$.

What is the molecular formula for hydralazine?

I did: \begin{align} 59.99~\ce{C}/12.011&=4.994\\ 5.03~\ce{H}/1.01&=4.9801\\ 34.98~\ce{N}/14.007&=2.4973. \end{align}

Then divided all $3$ by $2.4973$, and got 2 carbon, 2 hydrogen, and 1 nitrogen atoms i.e. $\ce{C_2H_2N}$. The online homework said that the stoichiometry was wrong. I don't know what I did wrong.

• Can you show your calculations that led you to that answer? That way someone can show you where you went wrong. – jonsca Jun 23 '14 at 0:50
• Good, but does the molecular weight of $\ce{C2H2N}$ add up to 160.178? If not, what do you need to multiply by to get there? – ron Jun 23 '14 at 1:12