Question #9c740

1 Answer
Jul 8, 2017

"55.5 g CaCl"_255.5 g CaCl2

Explanation:

For starters, notice that your sample contains

3.01 * 10^(23) = 1/2 * color(blue)(6.02 * 10^(23))3.011023=126.021023

formula units of calcium chloride. As you know, in order to have 11 mole of calcium chloride, you need to have a sample that contains color(blue)(6.02 * 10^(23))6.021023 formula units of calcium chloride -> this is known as Avogadro's constant.

In your case, the sample contains exactly half, 1/212, of a number equal to Avogadro's constant of formula units of calcium chloride, which means that it contains 0.50.5 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.