Chapter 7 Notes, Part I

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Chapter 7 Notes, Part I

• What is a mole?
• One Step Problems

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What is a mole?

• A furry, burrowing woodland creature, revered by
  many and adored by all?

Maybe!

• But not really in chemistry!

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A Mole...

• is a unit of measurement that tells how many
  particles of something you have!

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• much like a dozen (12), a gross (144) or a ream
  (500) is just a unit that groups smaller numbers
  into big ones...but its a big one a REALLY big
  one!

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1 mole 6.02 x 1023 particles!

• (thats a lot of flowers!)

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What are particles?

• Particles could be anything, but because of the
  size of the number, we usually mean

Atoms,
molecules, or
formula units.
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Avogadros Number

• The number 6.02 x 1023 is called Avogadros
  number.
• This is due to Amadeo Avagadros research leading
  to the discovery, not the discovery of the number
  itself.

It is a little known fact that Avogadro was voted
his classs most likely to have a scientific
discovery and most likely to look really creepy.
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Practice Problem 1

• How many moles are in 2.57 x 1025 atoms He?

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Practice Problem 2

• How many molecules of CO2 are in 25.3 moles?

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Moles and Volume

• It has also been discovered that 1 mole of all
  gases at a certain set of conditions called STP
  (standard temperature and pressure) have the same
  volume22.4L!
• So, 1 mole 22.4L (gas _at_ STP)

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Practice Problem 3

• How many moles of O2 are in 29.3L of O2 gas?

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Practice Problem 4

• If you have 3.6 moles of N2O (Nitrous oxide) how
  many liters would you have?

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Mass and Moles

• How do we usually measure out chemicals in a lab?

NOT by counting the number of particles!
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Mass and Moles

• We usually use mass to measure out chemicals.
• The problem with mass is that not all
  atoms or compounds have the same
  mass.

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Mass and Moles

• Avogadros number was established by using
  Carbon-12 as a standard. The number of particles
  in 12 grams of carbon 12 was set as 1 mole.

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Mass and Moles

• Conveniently, this is similar to how the atomic
  mass unit was established, so the atomic mass on
  the periodic table is also an elements molar
  mass (the mass of one mole of an element,
  measured in g/mol).

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What is the molar mass of...

• He
• Al
• Ba
• Rn

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Furthermore...

• Since compounds are just atoms bonded together,
  you can find the molar mass of a compound by
  adding together the molar mass of all the
  elements in the compound.

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What is the molar mass of...

• NaCl
• CO2
• Be3N2
• Ca(NO3)2

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Practice Problem 5

• How many grams of iron are in 3.5 moles?

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Practice Problem 6

• How many moles of Na2O are in 355.1g?