1. Molar Mass
Chemistry 11
Ms. McGrath

2. Molar Mass
Molar mass (M) is the mass of one mole (6.02 x 1023 particles) of a substance numerically equal to the element’s average atomic mass (u). It is expressed as g / mol.

3. Molar Mass
Molar masses of common chemical compounds that you might find in the chemistry laboratory can range between 18 grams/mole for compounds like water to hundreds of grams per mole for more complex chemical compounds.

4. Molar Mass
The lightest possible chemical that one can have under normal conditions is hydrogen gas, or H2. There is no limit to how heavy a chemical compound can be - it is not uncommon for macromolecules (large organic or bioorganic compounds such as DNA) to weigh thousands of grams per mole.

5. Molar Mass How do I find Molar Mass?
The molar mass of elements is found by looking at the atomic mass of the element on the periodic table. For example, if you want to find the molar mass of carbon, you would find the atomic mass of carbon on the periodic table, and this is equal to the molar mass in grams per mole. So, carbon has a molar mass of g / mol.

6. Molar Mass How do I find Molar Mass?
There are a few exceptions to this rule:
In the case of H, N, O, F, Cl, Br, and I, the element is diatomic, meaning that each molecule of the element has two atoms of that element bonded together.
P is normally found in clumps of four atoms, and S is found in clumps of eight atoms.
Aside from the exceptions above, all elements
have the same molar mass as the atomic masses
on the periodic table.

7. Molar Mass How do I find Molar Mass?
Molar masses of chemical compounds are equal to the sums of the atomic masses of all the atoms in one molecule of that compound. ex: BeO MBeO = 9.01 g/mol g/mol = g/mol

8. Molar Mass How do I find Molar Mass?
ex: Ca3(PO4)2
MCa x 3 = (40.08 g/mol) x 3
= g/mol
MP x 2 = (30.97 g/mol) x 2
= g/mol
MO x 8 = (16.00 g/mol) x 8
= g/mol
MCa3(PO4)2 = g/mol g/mol g/mol
= g/mol

9. Molar Mass Practice - Molar Mass
Page 57 #16, 17, 18, 19

10. Molar Mass Converting from Moles to Mass
Mass = Number of moles x Molar Mass m = n x M

11. Molar Mass Converting from Moles to Mass
A flask contains mol of carbon dioxide gas,
CO2. What mass of carbon dioxide gas is in this
sample?
m = n x M
MCO2 = 2 x (16.00 g/mol) g/mol
= g / mol
= (0.750 mol) x (44.01 g/mol)
= 33.0 g

12. Molar Mass Practice - Converting from Moles to Mass
Page 59 #20, 21, 22, 23

13. Molar Mass Converting from Mass to Moles
Number of moles = mass Molar Mass n = m M

14. Molar Mass Converting from Mass to Moles
How many moles of acetic acid, CH3COOH, are in a 23.6g sample? The molar mass of CH3COOH is: (12.01 x 2) + (16.00 x 2) + (1.01 x 4) = g / mol n = m M = 23.6 g g / mol = mol

15. Molar Mass Converting from Mass to Moles
Page 60 #