Lesson 15: Molar Mass
- The mass (in grams) of 1 mole of a substance is called the molar mass
- Determined from the atomic mass on the periodic table
- Measured in g/mol
Molar Mass of Compounds
- To determine the molar mass of a compound, add the mass of all the atoms together
Element Molar Mass
FeO 55.8 + 16.0 = 46.0 g/mol
H2O 2(1.0) + 16.0 + 18.0 g/mol
NaNO3 23.0 + 14.0 + 3(16.0) = 85.0 g/mol
Converting between MOLES & MASS
- To convert, we use molar mass as the conversion factor
- Be sure to cancel the appropriate units
How many grams is there in 2.2 mol of N2?
(2.2mol) (28g/1mol) = 62 g
How many moles are there in 131 g of NaO?
(131g) (1mol/39g) = 3.36 mol
How many moles are present in a 1.2 g sample of Ammonium Phosphate?
(NH4)3PO4 -> 3(14.0) + 12(1.0) + 31.0 + 4 (16.0) = 149
(1.2g) (1mol/149g) = 0.008 = 8.0 x 10^-3 mol
~ knipp
posted by chemistry11 @ 10:32 PM
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