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Unit 6


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Unit 6

  1. 1. Unit 6- The Mole 2011-2012
  2. 2. What is a mole? <ul><li>A.) A blind furry animal. </li></ul><ul><li>B.) A brown mark on your body. </li></ul><ul><li>C.) An important Chemistry concept. </li></ul><ul><li>D) A spicy Mexican sauce </li></ul><ul><li>E) A double agent (spy) </li></ul><ul><li>F.) All of these. </li></ul>
  3. 3. As you may have guessed, F is the correct answer!! Although a mole might be cute and fuzzy, we are going to focus on the Chemistry concept.
  4. 4. Counting Atoms <ul><li>Chemistry is a quantitative science - we need a &quot;counting unit.&quot; </li></ul><ul><li>The MOLE </li></ul><ul><li>1 mole is the amount of substance that contains as many particles (ions, atoms or molecules) as there are in 12.0 g of C-12. </li></ul>
  5. 5. A mole is a counting unit. Just like: <ul><li>12 eggs equals a dozen eggs </li></ul><ul><li>144 pencils equals one gross of pencils </li></ul><ul><li>60 seconds equals one minute </li></ul><ul><li>500 sheets of paper </li></ul><ul><li>equals one ream </li></ul>
  6. 6. One mole equals 6.022 x 10 23 particles <ul><li>So one mole of eggs would be 6.022 x 10 23 eggs </li></ul><ul><li>One mole of pencils would be 6.022 x 10 23 pencils </li></ul><ul><li>And so on... </li></ul><ul><li>THIS NUMBER IS ALSO CALLED “ AVOGADRO’S #” </li></ul>
  7. 7. Avogadro’s Number 6.02 x 10 23 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855). Amadeo Avogadro I didn’t discover it. Its just named after me!
  8. 8. Amadeo Avogadro (1776 – 1856) <ul><li>1 mole = 602 213 673 600 000 000 000 000 </li></ul><ul><li>or 6.022 x 10 23 </li></ul>thousands millions billions trillions quadrillions There is Avogadro's number of particles in a mole of any substance. Particles in a Mole Amedeo Avogadro (1766-1856) never knew his own number; it was named in his honor by a French scientist in 1909. its value was first estimated by Josef Loschmidt, an Austrian chemistry teacher, in 1895 . quintillions sextillions
  9. 9. THINKING ABOUT A MOLE! Can you give me an example to put that number in perspective? A computer that can count 10,000,000 atoms per second would take 2,000,000,000 years to count 1 mole of a substance.
  10. 10. Counting to 1 Mole Is that right? A computer counting 10 million atoms every second would need to count for 2 billion years to count just a single mole . Lets look at the mathematics. Therefore 1 year has 31,536,000 seconds or 3.1536 x 10 7 sec. A computer counting 10,000,000 atoms every second could count 3.153 x 10 14 atoms every year. Finally, 6.02 x 10 23 atoms divided by 3.1536 x 10 14 atoms every year equals 1,908,929,477 years or approximately 2 billion years! x sec = 1 year 365 days 1 year 1 day 24 hours 60 min 1 hour 60 sec 1 min = 31,536,000 sec
  11. 11. How Big is a Mole? One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles. One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 million times. It would take light 9500 years to travel from the bottom to the top of a stack of 1 mole of $1 bills.
  12. 12. What is all of this used for? <ul><li>Avogadro’s constant can be used to convert an amount of moles into the equivalent number of particles (atoms, molecules, ions) or grams . </li></ul><ul><li>This conversion is similar to changing 8 dozen eggs into the number of individual eggs. </li></ul><ul><li>Although this maybe easy to calculate quickly in your head or on your calculator, the following strategy will make it easier for you later in this unit </li></ul>
  13. 13. Mole Problem Solving Strategy Example: How many eggs are in 8 dozen? <ul><li>1. List what you know. (What was given in the problem?) </li></ul><ul><li>2. Setup the problem. Don’t forget your units and show every step. </li></ul><ul><li>3. NOW, and only now, use your calculator to verify the answer. </li></ul><ul><li>1. # of dozen = 8 dozen </li></ul><ul><li># of eggs = ? Eggs </li></ul><ul><li>2. </li></ul><ul><li>8 dozen x =?eggs </li></ul><ul><li>8 dozen x =?eggs </li></ul><ul><li>3. 8 x = 96 eggs </li></ul>
  14. 14. Looks easy right… Now you try one: How many pencils are in 9 gross? <ul><li>1. List what you know. (What was given in the problem?) </li></ul><ul><li>2. Setup the problem. Don’t forget your units and show every step. </li></ul><ul><li>3. NOW, and only now, use your calculator to verify the answer. </li></ul><ul><li>1. # of gross = 9 gross </li></ul><ul><li># of pencils = ?pencils </li></ul><ul><li>2. </li></ul><ul><li>9 gross X = ?pencils </li></ul><ul><li>9 gross X = ?pencils </li></ul><ul><li>3. 9 x = 1296 pencils </li></ul>
  15. 15. This strategy can be used with the mole concept. Problem: How many atoms are in 3.5 moles of Copper? <ul><li>1. The procedure is the same. List what you know. </li></ul><ul><li>2. Notice that 3.5 moles is in the numerator and then 1 mol is in the denominator. This allows you to cross out units. </li></ul><ul><li>3. Now calculate the answer. Does it make sense? </li></ul><ul><li>1. # of moles of Cu = 3.5 mol </li></ul><ul><li># of Cu atoms = ? </li></ul><ul><li>2. </li></ul><ul><li>3.5 mol Cu x </li></ul><ul><li>= ? atoms Cu </li></ul><ul><li>3.5 mol Cu x </li></ul><ul><li>= ? atoms Cu </li></ul><ul><li>3.5 x = = 2.1x 10 24 atoms Cu </li></ul>
  16. 16. You can also convert from atoms to moles… YEAH!! How many moles are in 3.01 x 10 23 atoms of Sodium? <ul><li>1. # of Na atoms = 3.01 x 10 23 atoms </li></ul><ul><li># of moles of Na = ? </li></ul><ul><li>2. 3.01 x 10 23 atoms x = ? mol Na </li></ul><ul><li>3.01 x 10 23 atoms x = ? mol Na </li></ul><ul><li>3. 3.01 x 10 23 x = 0.500 mol Na </li></ul>
  17. 17. It’s your turn again! How many atoms are in 7.5 mol of Argon? <ul><li>Before you start throwing down random numbers. Think about the problem. Should the final answer be bigger or smaller than 6.022 x 10 23 ? </li></ul><ul><li>Since 1 mole is 6.022 x 10 23 atoms, 7.5 moles has to be a larger number of atoms. </li></ul><ul><li>Thinking through the problem before you start it will allow you know if you solved the problem correctly. </li></ul>
  18. 18. Now calculate: How many atoms are in 7.5 mol of Argon? <ul><li>1. # of moles of Ar = 7.5 mol </li></ul><ul><li># of atoms of Ar = ? atoms </li></ul><ul><li>2. 7.5 mol Ar x = ? atoms Ar </li></ul><ul><li>7.5 mol Ar x = ? atoms Ar </li></ul><ul><li>3. 7.5 x = 4.52 x 10 24 atoms Ar </li></ul>
  19. 19. Now in small groups try the following practice problems <ul><li>1. How many atoms are present in 3.7 mol of sodium? </li></ul><ul><li>2. How many atoms are present in 155 mol of arsenic? </li></ul><ul><li>3. How many moles of xenon is 5.66 x 10 26 atoms? </li></ul>
  20. 20. If you showed all the steps, the correct answers are: <ul><li>1. 2.2 x 10 24 Na atoms </li></ul><ul><li>2. 9.33 x 10 25 As atoms </li></ul><ul><li>3. 940. mol Xe </li></ul>
  21. 21. Here are a few mole problem pointers: <ul><li>THINK about the problem before, after and while you are doing the problem. Does the answer make sense. Don’t just randomly plug in numbers into your calculator. </li></ul><ul><li>Follow the setup. I’m not doing this because I’m mean. (although you may disagree) This setup is the easiest and best way to always get the correct answer. </li></ul>
  22. 22. Now you are ready for some mole jokes! <ul><li>Who is Avogadro’s favorite actor? </li></ul><ul><li>Mol Gibson…. Get it? Ha ha </li></ul><ul><li>Where did Avogadro go on Saturday? </li></ul><ul><li>The shopping mole.. Wow these are funny! </li></ul><ul><li>What did Avogadro have on his pancakes? </li></ul><ul><li>Molasses!! I know you may think these jokes are remolting, but you will grow to love them!! </li></ul>
  23. 23. What did you say? One more mole joke? If you insist. <ul><li>Why did Avogadro look forward to the year 2000? </li></ul><ul><li>It was the start of the new molennium!!! </li></ul>