# Question #b8d89

Dec 21, 2017

From the formula, there are $3$ $\text{C}$ atoms for every $8$ $\text{H}$ atoms. So...

#### Explanation:

$5.60 \cdot {10}^{24} \text{H atoms" * "3 C atoms" / "8 H atoms} = 2.1 \cdot {10}^{24}$ $\text{C atoms}$

Now, to get to the mass of the sample, you must calculate the number of moles of ${\text{C"_3"H}}_{8}$ in the sample, and then use the molar mass of ${\text{C"_3"H}}_{8}$ to calculate the mass in grams:

$5.60 \cdot {10}^{24} {\text{H atoms" xx ("1 molecule C"_3"H"_8) / "8 H atoms" xx ("1 mole C"_3"H"_8) / (6.02xx10^23 "molecules") = "1.162 moles C"_3"H}}_{8}$

$\text{Molar mass" = 3 xx "12 g/mol" + 8 xx "1 g/mol" = "44 g/mol}$

So

${\text{Total mass" = "1.162 moles C"_3"H"_8 xx "44 g/mol" = "51.1 g C"_3"H}}_{8}$