Question #9c740

1 Answer
Jul 8, 2017

Answer:

#"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.