Question

Question #6effe

Answer 1

`2.4 * 10^(23)`

Explanation:

For starters, you know that every mole of glycerol contains

• three moles of carbon, `3 xx "C"`
• eight moles of hydrogen, `8 xx "H"`
• three moles of oxygen, `3 xx "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 * 10^(23)` atoms of hydrogen, as given by Avogadro's constant.

This means that your sample contains

`0.40 color(red)(cancel(color(black)("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.

Answer 2

`2.41 xx 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.

`0.050mol * 6.022 xx 10^23 ("units"/"mol") = 3.011 xx 10^22` molecules

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