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

7.4 - Calculation of Molar Mass

In section 7.1 we learned how to calculate the mass of a formula unit or a molecule. Now we will learn how to calculate the mass of 1 mole of substance. In section 7.3, we saw that the real neat thing about Avogadro's number is that:

We can equate the numerical quantity of mass of a single ATOM (in amu) to the mass of a mole of the same atoms (in grams).

or, when we are talking about molecules,

We can equate the numerical quantity of mass of a single MOLECULE to the mass of a mole of the same molecules (in grams).

For example:

1 water molecule, H2O

has a mass of 18.015 amu.

2 H atoms:
2 x 1.008 amu = 2.016 amu
1 O atom:
1 x 15.999 amu = 15.999 amu
Total mass:
18.015 amu







2 moles of H atoms:
2 x 1.008 grams = 2.016 grams
1 mole of O atom:
1 x 15.999 grams = 15.999 grams
Total mass:
18.015 grams
1 mole, or 6.022x 1023, of water molecules has a mass of 18.015 grams.

This is the molar mass of water.

The units of molar mass:

Let's take a look at the determination of the molar mass of sodium carbonate, Na2CO3.

 

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