Chapter 7 – Chemical
Quantities
The Mole: A Measurement of Matter
Mole-Mass and Mole-Volume Relationships
Percent Composition and Chemical
Formulas
7.1 The Mole: A Measurement of
Matter
 What is a Mole?
 No, not a furry rodent who digs in the
ground – at least not in chemistry…
 An amount used in measurements for
calculating chemical quantities.
 The Number of Particles in a Mole
 Mole = mol = Avogadro’s Number = 6.02
x 1023
 Moles can be used for representative
particles (Table 7.1).
7.1 The Mole: A Measurement of
Matter (cont.)
 The Mass of a Mole of an Element
 Gram atomic mass: the mass of an element expressed in
grams.
 e.g. Carbon (C) = 12.011 = 12.0 g
 Figure 7.8
7.1 The Mole: A Measurement of
Matter (cont.)

The Mass of a Mole of a Compound


Gram molecular mass (gmm) and gram formula mass (gfm)
e.g. H20 = 1+1+16 = 18g and for
NaCl = 23.0 + 35.5 = 58.5g
7.2 Mole-Mass and Mole-Volume
Relationships
 The Molar Mass of a Substance
 The amount of mass of any substance (in
grams) equal to one mole.
 Some confusion? Diatomic? Molecular
vs. Ionic compounds? Gaseous
elements?
 The Volume of a Mole of Gas
 STP = 0oC, 101.3 kPa or 1 atm
 Gases occupy a volume of 22.4L at STP
 Molar volume: 22.4L / mol
7.2 Mole-Mass and Mole-Volume
Relationships (cont.)
Chapter 7 Assignment
 CPQ’s # 1 p198
 44-51,55,56,57,59
7.3 Percent Composition &
Chemical Formulas
 Calculating the Percent Composition
of a Compound
 How much of each element/substance is
present in the whole? Percent
composition
 The relative amount of each element in a
compound – percent composition
 Equation: % mass (g) = (grams of E /
grams of compound ) x 100%
7.3 Percent Composition &
Chemical Formulas (cont.)
 Calculating Empirical Formulas
 Finding formulas from amount or percent
composition
 Empirical formula: the lowest whole-number
ratio of the atoms of the elements in a
compound.
 e.g. hydrogen peroxide = H2O2 with an empirical
formula of HO.
 Others: CO2, N2H4 = NH2, etc.
 Calculating Molecular Formulas
 Table 7.2
Ch 7 Assignments
 CPQ’s # 1 p198
 44-51,55,56,57,59
 Mole WS # 1
 CPQ’s # 2 p198
 60,61,64,65