Question

Question #9c740

Answer 1

`"55.5 g CaCl"_2`

Explanation:

For starters, notice that your sample contains

`3.01 * 10^(23) = 1/2 * color(blue)(6.02 * 10^(23))`

formula units of calcium chloride. As you know, in order to have `1` mole of calcium chloride, you need to have a sample that contains `color(blue)(6.02 * 10^(23))` formula units of calcium chloride `->` this is known as Avogadro's constant.

In your case, the sample contains exactly half, `1/2`, of a number equal to Avogadro's constant of formula units of calcium chloride, which means that it contains `0.5` moles of calcium chloride.

To convert the number of moles to grams, you must use the compound's molar mass.

You will end p with

`0.5 color(red)(cancel(color(black)("moles CaCl"_2))) * "110.98 g"/(1color(red)(cancel(color(black)("mole CaCl"_2)))) = color(darkgreen)(ul(color(black)("55.5 g")))`

The answer is rounded to three sig figs, the number of significant figures you have for the number of formula units present in the sample.