Unit #1Unit #2Unit #3Unit #4Unit #5Unit #6Unit #7Unit #8Unit #9Unit #10
spacerUNIT # 7  
spacerspacerIntroduction
spacerspacerObjectives
spacerspacerReading

spacer7.1 Calculation of
spacerFormula
spacerMass

spacer7.2 Mole
spacerConcept

spacer7.3 Atomic Mass
spacerRevisited

spacer7.4 Calculation of
spacerMolar Mass
spacer
7.5 Calculations
spacerinvolving
spacerAvogadro #

spacerMass to mole conversion and vice-versa
spacermole to number of particles conversion and vice-versa
spacerMass in grams to number of particles conversion
spacer
7.6 Molar Volume
spacerof a Gas
spacerMolar volume calculations
spacer
7.7 Percent
spacerComposition
spacer
7.8 Empirical
spacerFormula

spacer7.9 Empirical
spacerMass to
spacerMolecular
spacerFormula



spacerProblems
spacer1 | 2
| 3 | 4 | 5

Unit #7 CALCULATIONS BASED ON FORMULAE

7.2 - Mole Concept

The scientific definition of a mole is as follows:

  • 1 mole of 12C is exactly 12 grams.
    (in section 3.2 we learned that carbon-12 is a naturally occurring isotope of carbon)
  • 1 mole of any substance contains 6.022 x 1023 particles (rounded to 4 significant figures).

In the above definition, do you realize that when we talk about the mole,

  • it has an equivalent mass (1 mole = 12 grams 12C)
  • it is a counting unit, a quantitiy of things (1 mole of any substance contains 6.022 x 1023 particles)
Want to see this number written out in l-o-o-n-n-g form?
Click here.



Why do we use the mole as a counting unit?


4 good reasons!

  1. In chemistry, the particles that make up matter are very small (section 3.1). So, counting by the mole is convenient.
  2. We need to scale up to see what we are working with.
  3. We need to scale up to do laboratory work.
  4. In chemistry, we count by weighing.

Section 8.1
Calculation of Mole of Units. Avogadro's Number (N) ..p189

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