Question

Howe would you calculate the number of moles of Cl atoms in `3.61x10^24` formula units of magnesium chloride, `MgCl_2`?

Answer 1

Use Avogadro’s number to calculate the number of moles of `MgCl_2`. The number of moles of Cl is twice as much, because the ratio of Cl in `MgCl_2` to `MgCl_2` is 2:1.

`(3.61*10^24)/(6.022*10^23) = 5.99`
Therefore, there are 12 moles of Cl.

Answer 2

There are `7.22xx10^24` atoms `"Cl"` in `3.61xx10^24` formula units of `"MgCl"_2"`.

Explanation:

Each formula unit of magnesium chloride, `"MgCl"_2"`, contains two chlorine, `"Cl"`, atoms.

Multiply the number of formula units by the conversion factor

`(2color(white)(.)"atoms Cl")/(1color(white)(.)"formula unit MgCl"_2`.

`3.61xx10^24color(red)cancel(color(black)("formula units MgCl"_2))xx(2color(white)(.)"atoms Cl")/(1color(red)cancel(color(black)("formula units MgCl"_2)))=7.22xx10^24"Cl atoms"`