Question #33cb2
1 Answer
Explanation:
The first thing to do here is figure out how many formula units of calcium chloride,
To do that, you must use the definition of a mole, which as you know is simply a very, very large collections of atoms. More specifically, in order to have one mole of an ionic compound, you need to have
color(blue)(|bar(ul(color(white)(a/a)"1 mole" = 6.022 * 10^(23)"f units"color(white)(a/a)|))) -> Avogadro's number
Now, your sample will contain a total of
3 color(red)(cancel(color(black)("moles CaCl"_2))) * (6.022 * 10^(23)"f units CaCl"_2)/(1color(red)(cancel(color(black)("mole CaCl"_2)))) = 1.8 * 10^(24)"f units CaCl"_2
As you know, a formula unit of calcium chloride is made up of
- one atom of calcium,
1 xx "Ca" - two atoms of chlorine,
2 xx "Cl"
Since every formula unit of calcium chloride contains one atom of calcium, it follows that your answer will be
1.8 * 10^(24) color(red)(cancel(color(black)("f units CaCl"_2))) * "1 atom Ca"/(1color(red)(cancel(color(black)("f unit CaCl"_2)))) = color(green)(|bar(ul(color(white)(a/a)color(black)(2 * 10^(24)"atoms of Ca")color(white)(a/a)|)))
The answer is rounded to one sig fig, the number of sig figs you have for the number of moles of calcium chloride.
