Stoichiometry –

- the study of the quantitative aspects of chemical reactions

The mole –

- A counting unit
- Similar to a dozen, except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000
- 6.02 X 10 to the 23 power (in scientific notation)

How big is the Mole?

- Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles.
- If you had Avogadro’s number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to the of over 9 miles.
- If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

Where did it come form?

- It was NOT just picked. It was MEASURED
- One of the better methods of measuring this number was the Millikan Oil Drop Experiment
- Since then we have found even better ways of measuring using x-ray technology

The Mole

- 1 dozen cookies= 12 cookies
- 1 mole of cookies = 6.02 X 10 to the 23 power cookies
- 1 dozen cars = 12 cars
- 1 mole of cars = 6.02 X 10 to the 23 power cars
- 1 dozen Al atoms= 12 Al atoms
- 1 mole of Al atoms =6.02 X 10 to the 23 power atoms
- Note that the number is always the same, but the mass is very different.
- Mole is abbreviated mol

Molar Mass

- The Mass of 1 mole (in grams)
- Equal to the numerical value of the average atomic mass
- 1 mole of C atoms = 12.0 g
- 1 mole of Mg atoms = 24.3 g
- 1 mole of Cu atoms = 63.5

Other Name Related to Molar Mass

- Molecular Mass/ Molecular Weight: If you have a single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different.
- Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different.
- The Point: you may hear all of these terms which mean the same number… just different unites

Converting Moles and Grams

- Aluminum is often used for the structure of light-weigt bicycle frames.

Types of Formulas

- Empirical formula: the formula of a compound that expresses the smallest whole number ratio of the atoms present.
- ionic formula are always empirical formulas.
- Molecular Formula: the formula that states the actual number of each kind of atom found in one molecule of the compound.

To obtain an Empirical Formula

- Determine the mass in grams of each element present, if necessary.
- Calculate the number of moles of each element.
- Divide each by the smallest number of moles to obtain the simplest whole number ratio.
- If whole numbers are not obtained in step 3, multiply through by the smallest number that will give all whole number.

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