# What is the percent by mass of hydrogen in aspirin, C_9H_8O_4?

##### 1 Answer
Jan 17, 2018

5.035%

#### Explanation:

We first need to find the molar mass of aspirin, which is $180.157 g \text{/} m o l$. A hydrogen atom has a molar mass of $1.008 g \text{/} m o l$. There are $9$ hydrogen atoms, so they have a total molar mass of $1.008 \cdot 9 = 9.072 g \text{/} m o l$.

So, the mass of hydrogen accounts for

9.072/180.157*100%~~5.035%

the mass of aspirin $\left({C}_{9} {H}_{8} {O}_{4}\right)$.