Question

What is the mass percent of hydrogen for `C_3H_5OH`?

Answer 1

`color(red)(10.41%)`

Explanation:

In order to compute the mass percent of hydrogen in `C_3H_5OH` we're going to need two things:

`color(brown) "1: The formula mass of the entire compound"`
`color(brown) "2: The atomic mass of hydrogen"`

The formula mass of `C_3H_5OH` is `58.08 g/(mol)` because:

`3(12.01g/(mol)) + 6(1.008g/"mol") + (16.00 g/"mol")` `= 58.08 g/(mol)`

The atomic mass of the hydrogen atom is `1.008 g/(mol)`

Now, we have to use the following equation:

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The numerator represents the mass of the desired atom, which is H in our case, and the denominator represents the mass of the entire compound. You just divide the two and multiply by 100 to obtain the percent composition:

`"Mass of H"/("Molar Mass of C"_3"H"_5"OH") xx100%`

`"(6)1.008 g/mol"/"58.08g/mol"xx100% = 10.41%`

I multiplied the atomic mass of hydrogen by 6 because you have to account for all of the hydrogen atoms in the formula.