MOLAR MASSUsing Molar Mass as a

Conversion Factor

Molar Mass A molar mass is the mass in grams of one mole of

a substance. One mole of any substance contains Avogadro’s number of

particles. 6.022 x 1023 particles.

Calculated by adding together the masses of all of the individual atoms in a chemical formula. Units are grams per mole (g/mol).

Example – KClO3

K = 39.10g x 1 atom = 39.10g Cl = 35.45g x 1 atom = 35.45g O = 16.00g x 3 atoms = 48.00g 39.10 + 35.45 + 48.00 = 122.55 g KClO3

Practice Problems

Complete practice problems. Solutions:

H2SO4 = 98.09 g Ca(NO3)2 = 164.10 g PO4

3- = 94.97 g MgCl2 = 95.21 g Na2SO3 = 126.06 g HClO3 = 84.46 g MnO4

- = 118.94 g C2H6O = 46.08 g

Molar Mass as a Conversion Factor

Molar mass can be used to convert between: Moles of a substance and grams of a

substance. Grams of a substance and moles of a

substance.

Equations: x = grams x = moles

Converting Moles to GramsWhat is the mass in grams of 2.50mol of oxygen

gas (O2)? Step 1: Calculate molar mass.

16.00 + 16.00 = 32.00 g Step 2: Use equation:

x = 80.0 g O2

Solutions: 2. 51.87g NH3

3. 43g Ca(NO3)2

4. 1,303g Fe2(SO4)3

Converting Grams to MolesHow many moles are there in 3.82g of sulfur dioxide(SO2)? Step 1: Calculate molar mass.

32.07 + 16.00 + 16.00 = 64.07 g Step 2: Use equation:

x = 0.0596 mol SO2

Solutions: 2. 2.385 mol 3. 1.09 mol 4. 0.25 mol