Chapter 4: Calculations Used in
Analytical Chemistry
CHE 321: Quantitative Chemical Analysis
Dr. Jerome Williams, Ph.D.
Saint Leo University
Overview
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Units & SI System
Moles & Millimoles
Solutions: Expressing Concentration
Stoichiometry
Units & SI System
• Units convey information and serve as guide
to solving problems
– Fundamental Units
– Derived Units
Table 4-1 p63
Units & SI System
• Measurements based on SI system, which is
metric system
– Metric Prefixes
– Performing Unit Conversions (see Tutorials)
Table 4-2 p63
Moles & Millimoles
• Mass versus Weight
• Moles are the SI unit for amount of a
substance.
• One mole of anything contains Avogadro’s
number of particles (chemical formula)
p64
Moles & Millimoles
• Molar Mass is mass in grams of one mole of a
substance.
• Calculate molar mass by summing atomic masses of
all elements in formula.
• Often more convenient to use unit millimole (Note: 1
mmole is equivalent to 10-3 mole)
p65
Moles & Millimoles
• Review Examples 4.1 & 4.2
• Complete Tutorials
Solutions: Expressing Concentration
• Review definitions of analytical molarity, and
equilibrium molarity
– Equilibrium concentrations expressed as molarity
– Analytical concentrations use formal concentration
• Review Examples 4.4 – 4.6
• Review Tutorials
Solutions: Expressing Concentration
• Percent Concentration - review definitions & formulas for the
following
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Mass (Weight)%
Volume %
Weight/volume %
Parts per Million (ppm)
Parts per Billion (ppb)
• Go over example problems & complete tutorials
Solutions: Expressing Concentration
• Review definitions of p-Functions
pX = - log [ X ]
Solutions: Expressing Concentration
• Review definitions of density and specific gravity
• Density = mass / volume
• M1 V1 = M2 V2
Figure 4-1 p74
Table 4-3 p74
Stoichiometry
• Quantitative relationship among reactants &
products in a balanced chemical reaction.
• Review Empirical vs. Molecular Formulas
• Review Structural Formulas
Figure 4-2 p76
Suggested Problems
• HW Set 2:
4.1, 4.4, 4.7-4.15 (odd)
• HW Set 3:
4.17, 4.20, 4.23, 4.31, 4.35