Question

How many carbon atoms are there in 0.0418 g of carbon dioxide?

Answer 1

Find the number of mols of CO2
1 mol of CO2 has a mass of
1 C + 2Os = 12 + 2*16 grams = 44 grams
x mol =0.0418 CO2

1/x = 44/0.0418
44x = 0.0418
x = 0.0418 / 44 
x =  0.00095 mol

1 mol of CO2 has 6.02 * 10^23 Carbon atoms in it. Note that is the same number of molecules of CO2 present.
0.00095 mols = x

1/0.00095 = 6.02*10^23) / x
x = 6.02*10^23 * 0.00095
x = 5.719 * 10^20  atoms of carbon in 0.0418 grams of CO2