7. The mass of a sample of Co, is 91.72 g. How many molecules does it contain?

9.370 x 10 to the 23 molecules

Explanation:

91.72/1 x 1 mole Co/58.933g x 6.02 x 10 to the 23/1 mole Co

Mass 1 mole of CO

C = 12

O = 16

m = 28

Mols of 91.72 grams

m = given Mass / Molar Mass

m = 91.72 / 28

m = 3.28 mols

Molecules

1 mol of anything is 6.02 * 10^23 molecules (in this case)

3.28 mol of CO = x

1/3.28 = 6.02*10^23/x Cross multiply

x = 3.28 * 6.02 * 10^23

x = 1.97 * 10^24