Chapter 6 Notes
Chem210FL
page 1
Dr. Lara Baxley
Chapter 7 Notes: Chemical Quantities
I. The Mole Learning Goal Use Avogadro's number to determine the number of
particles in a mole
A. Definition of a Mole
How many eggs in a dozen? _____
How many sodas in a case? _____
How many pages in a ream? _____
How many atoms in a mole? ________________
B. Avogadro’s Number as a Conversion Factor
Write two conversion factors using Avogrado’s number.
Example: How many molecules of water are in 9.34 mol water?
C. Moles of Elements in Chemical Formulas
Subscripts in chemical formula indicate the__________________________________
Example: H2O: 1 mole of water contains ________________________________
Practice
1. How many moles of chlorine is in 34.2 mole CCl4?
2. How many carbon atoms are in 2.133 mol of aspirin, C9H8O4?
Chapter 6 Notes
Chem210FL
page 2
Dr. Lara Baxley
II. Molar Mass Learning Goal Determine the molar mass of a given substance.
A. Molar Mass:
B. Molar Mass of a Compound: The sum of the molar masses of the elements in
the compound
Practice
1. What is the molar mass of CaCl2.
2. Calculate the molar mass of calcium phosphate.
III. Calculations using the Molar Mass Learning Goal Use molar mass to calculate
moles from grams or grams from moles.
Example
How many moles of magnesium are in 12.34 g?
Chapter 6 Notes
Chem210FL
page 3
Dr. Lara Baxley
Practice
1. What is the mass, in grams, of 0.0215 moles of Mg(NO3)2?
2. How many moles of sodium atoms are in 13.42 g sodium oxide?
IV. Mass Percent and Empirical Formulas Learning Goals 1) Calculate the mass %
of each element in a compound, 2) Use experimental data to determine the
empirical formula of a compound.
A. Mass Percent
mass % = (no. of atoms of element)(mass element) x 100
mass compound
Chapter 6 Notes
Chem210FL
page 4
Dr. Lara Baxley
Practice: Calculate the mass percent of bromine in lead (II) bromite.
B. Empirical formula: ____________________________________________________
Example: Write the empirical formulas for the following compounds:
a) C2H6
b) C6H12O6
c) CO2
d) C5H10O5
Determining an Empirical Formula from Data:
In order to determine the empirical formula of a compound from data, you must
1) Determine the moles of each element in the sample
2) From the moles of each element, determine the lowest whole number ratio
Examples
1. A sample of a compound was found to contain 5.88 g C, 0.987 g H, and 3.133 g O.
What is the empirical formula of the compound?
Chapter 6 Notes
Chem210FL
page 5
Dr. Lara Baxley
2. An analysis of the pigment in school bus paint shows a composition of 17.5% Na,
39.7% Cr, and 42.8% O. What is the empirical formula of this compound?
V. Molecular Formulas Learning Goal Determine the molecular formula using the
empirical formula and molar mass
Molecular Formula: Actual number of atoms of each element in a molecule
empirical
molecular
integer x empirical = molecular
formula
CH3
C2H6
2(CH3) = C2H6
molar mass
15.034
30.068
2(15.034) = 30.068
integer = molecular mass
empirical mass
Practice
What is the molecular formula of a compound if its molar mass is 112.21 g/mol and
its empirical formula is CH2?
Suggested textbook problems:
Ch7: Within Chapter: 1,3,5,7,9,13,19,23,27,31,33,35,37,39,41,43,*45,*47,*49
End of Chapter: 51,53,55,63,65,67,*69,*75