Moles and Molar Calculations

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Chapter 7
Moles and Molar Calculations
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Number of Particles in a Mole

• Avogadros Number

• 1 mole 6.02 X 10 23 representative
• particles. (atom, molecule, etc.)

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What is a mole?
- It is just a word that means a number.
6.02 x 1023
- Just like a dozen
20
- A score
144
- A gross
- A furlong
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Mass of a Mole of an Element

• Gram Atomic masses (find them on the periodic
  table for single elements).

• This is the mass of one mole of that element.

• You can change the label from amu to
• grams because there are 6.02 x 1023amu
• in a gram

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How to find gram atomic masses

• Also called formula masses/weight, molecular
  masses/weight

Ex. C2O6H6
C 2 x 12.011g 24.022g H 6 x 1.00794g
6.04764g O 6 x 15.9994g 95.9964g 24.022g
6.04764g 95.9964g 126.07g
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Mole-Mass and Mole-Volume Relationships

• Molar mass Mass of one mole of a substance

• This means it is not the mass of one
• molecule it is the mass of 6.02 x 1023
• molecules.

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Mole Road Map

• Page 186
• CHEMASAP
• Posterboard example

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Volume of a Mole of Gas

• Volume of a gas is measured at STP (standard
  temperature and pressure)

- STP 0 Celcius, 1 atmosphere (101.3 kPa) -
At STP 1 mole gas 22.4 liters
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Composition and Chemical Formulas

• composition the relative amounts of each
  element in a compound.

To find the percent composition for the elements
in a chemical formula you would 1. Find the
molecular mass of each element in the
compound 2. Add all of the masses to get the
molecular mass. 3. Divide the mass of each
element by the molar mass of the molecule and
multiply by 100
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Calculating Empirical Formulas

• Empirical Formula Lowest whole number ratio
  of the atoms of elements in the compound
• Worksheet will be given on how to calculate
  empirical formulas from .

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Calculating Molecular Masses

• Can calculate molecular formulas from the given
  empirical formula.
• Ex HO H2O2
• Some empirical and molecular formulas are the
  same.