THE MOLE WORKSHEET
1. What is a mole of a substance?
A mole of a substance is 6.02 x 1023 entities (atoms or molecules) of a substance. Therefore, one
mole of oxygen has 6.02 x 1023 atoms, which will then have a mass of 16.00 g.
2. What does the term molar mass mean?
A molar mass is the mass of one mole of a substance. Oxygen has a molar mass of 16.00 g/mol
(for every mole of oxygen there is, it weighs 16.00 g).
3. What is the mass of the following substances?
(a) 3.7 mol of K
b) 0.0067 mol of SO2
m=nxM
= 3.7 mol x 39.10 g/mol
= 144.67 g
m=nxM
= 0.0067 mol x 64.06 g/mol
= 0.43 g
4. Determine the number of moles of substance represented by each of the following masses.
(a) 5.6 g of He
(b) 67 g of MgCl2
n=m/M
= 5.6 g / 4.0 g/mol
= 1.4 mol
n=m/M
= 67 g / 95.21 g/mol
= 0.703 mol
5. How many atoms or molecules are present in each of the following? (Hint: Use Avogadro’s
constant)
(Note: If you are working with an element, you are calculating for the # of atoms. If you are
working with a compound, you are calculating for the # of molecules).
a) 2.0 mol Ne
b) 4.5 g H2O
# atoms = nNe x 6.02 x 1023 atoms
1 mol
= 2.0 mol x 6.02 x 1023 atoms
1 mol
24
= 1.2 x 10 atoms
# molecules = nH2O x 6.02 x 1023 molecules
c) 0.7 mol CO2
# molecules = nCO2 x 6.02 x 1023 molecules
1 mol
= 0.7 mol x 6.02 x 1023 molecules
1 mol
= 4.21 x 1023 molecules
= nH2O x 6.02 x 1023 molecules
1 mol
= mH2O x 6.02 x 1023 molecules
MH2O
1 mol
= 4.5 g
x 6.02 x 1023 molecules
18.02 g/mol
1 mol
23
= 1.50 x 10 molecules