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Some Revision

Some Revision. http://science- cochrane.wikispaces.com/New+Revision+Forums. Today’s Lesson. Some Housekeeping Ar , Mr & All That Jazz So what are those chemical thingies called when you put them together??. The Mole. The mole is used to tell us the mass of a particular number of atoms.

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Some Revision

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  1. Some Revision http://science-cochrane.wikispaces.com/New+Revision+Forums

  2. Today’s Lesson • Some Housekeeping • Ar, Mr & All That Jazz • So what are those chemical thingies called when you put them together??

  3. The Mole • The mole is used to tell us the mass of a particular number of atoms. • There are 6.02 X 10^23 atoms in a mole. • When you look at the periodic table, the molecular mass tells you how much 1 mol of that atom weighs. • For example, 1 mol of Hydrogen = 2 grams I was not talking about this mole!! http://crashofcourse.blogspot.com/2010/06/mole-attack.html

  4. The Mole in Liquids • In Chemistry, you might notice that liquids have 1M, 10M, 0.1M on them. • This tells us how many moles of an element or compound are dissolved in 1L of water. • As such, 1M is 10 times stronger than 0.1M etc. http://www.thinkgeek.com/tshirts-apparel/unisex/sciencemath/e635/

  5. Relative Atomic Mass • The relative atomic mass (or Ar), is the average mass of an atom. • Different elements might have different weights due to different isotopes (such as Cl having isotopes with an atomic mass of 35 & 37). • We work it out through percentages (bottom right hand corner of P110)

  6. Relative Formula Mass • The relative formula mass (Mr), is the mass of a compound. It’s just the Ar of the whole compound like below. • C4H4O2 is a compound. It’s worked out the following way. • C = 12, H = 1, O = 16. • So 12 X 4 + 4 X 1 + 16 X 2 = 68

  7. Mass & Moles • Working out the mass from the number of moles is easy. You use the following rules. • Mass of Element = Number of Moles X Ar • Mass of Compound = Number of Moles X Mr • Moles of Element = Mass / Ar • Moles of Compound = Mass / Mr

  8. An Example • I have 20 grams of Magnesium Oxide (MgO). How many moles do I have? • Mr of MgO • Mg = 24 g, O = 16 g • 24 + 16 = 40 g • Moles = 20 g of MgO / 40g (Mr) • We have 0.5 Moles of MgO

  9. Some Reminding • In a Chemical Reaction, it often works like this: • A + B  C + D • A + B are the reactants • C + D are the products • Balance the reactants and products. Make sure there is the same amount of atoms and charge on each side! http://www.digitalphotographybasics.com/wp-content/uploads/product-photography.jpg

  10. Small Trick For Chemical Reactions • Here is a small trick that can come in handy. Remember that it’s just a trick, and does not always work. • AB + CD  AD + BC • Eg; NaOH + HCl  NaCl + H2O • A = Na. B = OH, C = H, D=Cl • The cation (or positive charged ion) always goes first

  11. Ultra Fun Worksheet • I’ll now do some more examples on the board for notes – fun fun!! • We will also complete the worksheets handed out.

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