# Question 6effe

Jun 17, 2017

$2.4 \cdot {10}^{23}$

#### Explanation:

For starters, you know that every mole of glycerol contains

• three moles of carbon, $3 \times \text{C}$
• eight moles of hydrogen, $8 \times \text{H}$
• three moles of oxygen, $3 \times \text{O}$

This means that your sample contains

0.050 color(red)(cancel(color(black)("moles C"_3"H"_8"O"_3))) * "8 moles H"/(1color(red)(cancel(color(black)("mole C"_3"H"_8"O"_3)))) = "0.40 moles H"

Now, in order to find the number of atoms of hydrogen, use the fact that every mole of elemental hydrogen contains $6.022 \cdot {10}^{23}$ atoms of hydrogen, as given by Avogadro's constant.

This means that your sample contains

$0.40 \textcolor{red}{\cancel{\textcolor{b l a c k}{\text{moles H"))) * (6.022 * 10^(23)color(white)(.)"atoms H")/(1color(red)(cancel(color(black)("mole H")))) = color(darkgreen)(ul(color(black)(2.4 * 10^(23)color(white)(.)"atoms H}}}}$

The answer is rounded to two sig figs, the number of sig figs you have for the number of moles of glycerol.

Jun 18, 2017

$2.41 \times {10}^{23}$

#### Explanation:

First we use Avogadro’s number to find out how many individual molecules there are. Then we multiply that value by the number of hydrogen atoms in the molecule.

$0.050 m o l \cdot 6.022 \times {10}^{23} \left(\text{units"/"mol}\right) = 3.011 \times {10}^{22}$ molecules

3.011 xx 10^22 "molecules" * 8 ((H "atom")/"molecule") = 2.41 xx 10^23# hydrogen atoms