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Ch. 10 “The Mole”

Ch. 10 “The Mole”. 6.02 X 10 23. SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!. 1 mol = molar mass. 1 mole = 22.4 L @ STP.

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Ch. 10 “The Mole”

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  1. Ch. 10 “The Mole” 6.02 X 1023 SAVE PAPER AND INK!!! When you print out the notes on PowerPoint, print "Handouts" instead of "Slides" in the print setup. Also, turn off the backgrounds (Tools>Options>Print>UNcheck "Background Printing")!

  2. 1 mol = molar mass 1 mole = 22.4 L @ STP 1 mol = 6.02 x 1023 particles Welcome to Mole Island

  3. We will use the mole interpretation! Chemical equations can be interpreted in many ways! Which interpretations support the Law of Conservation of Mass? Atoms & Mass! Only mass & Atoms are conserved in every reaction!

  4. Chemical Equations are simple. 2H2 + O2 2H2O Chemical equations are quite easy. Here we count out 4 hydrogens and 2 oxygen atoms and we can make two water molecules. But how many hydrogens and oxygens would we count out to make enough water to fill a one liter bottle of water?

  5. Imagine the number of grains of sand in a handful of sand: thousands or maybe a million? It would be difficult to count that many. Now imagine the number of grains of sand that would be present if we covered all of the Earth (land and sea) 10 miles deep with sand. That number of grains of sands is the same number of water molecules needed to fill a 1 liter bottle!

  6. The Art of Counting Without Counting

  7. COUNTING COINS WITHOUT COUNTING

  8. How Scientists Keep Track of Atoms • One way to measure the amount of a substance available is to count the # of particles in that sample • However, atoms & molecules are extremely small • and, the # of individual particles in even a small sample is very large • Therefore, counting the # of particles is not a practical measure of amount • To solve this problem, scientists developed the concept of the mole • It’s the “chemical counting unit”

  9. Just as a dozen eggs equals 12 eggs, • a Mole = 6.02 x 1023602,000,000,000,000,000,000,000 • It is equal to that number no matter what kind of particles you’re counting! • It could represent donuts, pens, bikes, atoms, molecules, etc. The word “mole” was introduced about 1896 by Wilhelm Oswald, who derived the term from the Latin word moles meaning a “heap” or “pile.” • The mole is theSI base unit formeasuringthe amount of a substance.

  10. Avogadro’s Number • 6.02 X 1023 • This number is named in honor of Amadeo Avogadro (1776 – 1856),who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present under certain conditions.

  11. The Mole • 1 moleof anything = 6.022 ´ 1023units of that thing • 6.022 ´ 1023 is equal to the number of carbon atoms in exactly 12 grams of pure carbon-12.

  12. Oxygen 32.00 g One mole of common substances. Water 18.02 g CaCO3 100.09 g Copper 63.55 g

  13. The Mole This photograph shows one mole of solid (NaCl), liquid (H2O), and N2 gas.

  14. Mass and Moles of a Substance 1-octanol (C8H17OH) Mercury(II) Iodide (HgI2) One mole of different substances. Sulfur (S8) Methanol (CH3OH)

  15. 1 Mole of Particles

  16. Also known as: The ‘Get-a-Life’ Syndrome! Exactly How Big is a Mole? Q: How long would it take to spend a mole of $1 coins if they were being spent at a rate of 1 billion per second?

  17. A Mollionaire A: If a mole of $1 coins were being spent at a rate of 1 billion per second: $ 6.02 x 1023 / $1 000 000 000 = 6.02 x 1014 payments = 6.02 x 1014 seconds 6.02 x 1014 seconds / 60 = 1.003 x 1013 minutes 1.003 x 1013 minutes /60 = 1.672 x 1011 hours 1.672 x 1011 hours / 24 = 6.968 x 109 days 6.968 x 109 days / 365.25 = 1.908 x 107 years A: It would take 19 million years

  18. Just How Big is a 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 a depth 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.

  19. More Examples, please! 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.

  20. Reminder: The Mole is just a counting number! • 1 dozen cookies = 12 cookies • 1 mole of cookies = 6.02 X 1023 cookies • 1 dozen cars = 12 cars • 1 mole of cars = 6.02 X 1023 cars • 1 dozen Al atoms = 12 Al atoms • 1 mole of Al atoms = 6.02 X 1023 atoms Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

  21. Yummm! Donuts! I love chemistry! How Do We Use The Mole? • We never use the mole to describe macroscopic or real world objects. • 1 mole (6.02x1023) of watermelon seeds would be found inside a watermelon the size of the moon. • 1 mole (6.02x1023) of donut holes would cover the earth and would be 5 miles deep. • Since the mole is such a huge number of items, it is only used to describe the amount of things that are very, very small. • 1 mole (6.02x1023) of water molecules would barely fill a shot glass

  22. A Mole of ParticlesContains 6.02 x 1023 particles = 6.02 x 1023C atoms = 6.02 x 1023H2O molecules = 6.02 x 1023NaCl formula units (6.02 x 1023 Na+ ions and 6.02 x 1023Cl– ions) 1 mole C 1 mole H2O 1 mole NaCl

  23. The Mole 1 amu = 1.66054 x 10-24 g 1 g = 6.02214 x 1023 amu Same #, different unit label!

  24. Learning Check Suppose we invented a new counting unit called a “Salb” and one Salb contains 8 objects. 1. How many paper clips in 1 Salb? a) 1 b) 4 c) 8 2. How many oranges in 2.0 Salbs? a) 4 b) 8 c) 16 3. How many Salbs contain 40 gummy bears? a) 5 b) 10 c) 20

  25. We can use Avogadro’s # in Conversion Factors Oh, Goody! 6.02 x 1023 particles 1 mole or 1 mole 6.02 x 1023 particles Note that a “particle” can be an atom, molecule, formula unit, or ion!

  26. CHEMICAL REP. PARTICLE REPRESENTATIVE SUBTANCE FORMULA PARTICLE IN 1 MOL

  27. Converting Between Moles and Particles

  28. How we measure moles… • Do you know how to measure out 3 moles of sugar or salt or water? • The mole is a counting unit, so we would have to count out 6.02x1023 particles of each substance. (no thank you) • There are 2 ways we can use to measure out a number of moles of • a substance. • Measure it ingrams(amass) • Or measure it inliters(avolume)

  29. Learning Check 1. Number of atoms in 0.500 mole of Al a) 500 Al atoms b) 6.02 x 1023 Al atoms c) 3.01 x 1023 Alatoms 6.02 x 1023 atoms Al 0.500 mol Al = 1 mole Al 3.01 X 1023 atoms Al

  30. 2.Number of moles of S in 1.8 x 1024 S atoms a) 1.0 mole S atoms b) 3.0 mole S atoms c) 1.1 x 1048 mole S atoms 1.8 x 1024 atoms S 1 mole S = 6.02 x 1023 atoms S 3.0 moles S

  31. Let’s look at Mass of Particles • Atomic Mass: The mass of an atom (measured in amu’s.) • Molecular Mass: the sum of atomic masses of • all atoms in a molecule (measured in amu’s.) • example: H2O has a formula mass of 18.0 a.m.u • Formula Mass: Sum of the mass of atoms in a formula unit of an ionic compound (measured in amu’s.) example: NaCl has a formula mass of 58.5 a.m.u.

  32. NaCl NaCl 58.5 amu Formula mass is the sum of the atomic masses (in amu) in a formula unit of an ionic compound. Na 1 x 23.0 amu = 23.0 Cl 1 x 35.5 amu = 35.5

  33. SO2 SO2 64.1 amu S 1 x32.1 amu = 32.1 O 2 x 16.0 amu = 32.0 Molecular mass is the sum of the atomic masses (in amu) in a molecule.

  34. We already know that 1 atom of C-12 has a mass of 2.010 x 10-23 g. (This is also equal to 12 amu!) We also want the atomic mass of 12.0 amu to become 12.0 g. Let’s review what we already know…….. So, the problem becomes this…….. 2.010 x 10-23 g/atom C-12 x ? atoms = 12.0 g C-12

  35. Why not use the average atomic mass that is already on the periodic table? It is already a relative mass, right? Why reinvent the wheel?

  36. But the atomic mass on the chart is in AMU, not grams! We do not have an AMU balance!

  37. Then let’s convert the number on the periodic chart from AMU to grams!

  38. Molar Mass A substance’s molar mass is it’s formula mass in grams. CO2 = 44.01 grams per mole H2O = 18.02 grams per mole Ca(OH)2 = 74.10 grams per mole C = 12.0 g/mole

  39. Calculating molar masses using chemical formulas What is the mass of 1 mole of C6H12O6? • The overall mass of 1 mole of C6H12O6 will be the molar mass of 6 Carbons + the molar mass of 12 Hydrogens + the molar mass of 6 Oxygens. 6 Carbons = 6 * 12.011 g = 72.066 g 12 Hydrogens = 12 * 1.0079 g = 12.095 g 6 Oxygens = 6 * 15.999 g = 95. 994 g 180.16 g/mole

  40. Periodic Table of the Elements The numbers under the element names are the relative weights. However, if you consider one mole of the element (6 x 1023 atoms) then these numbers are read as grams.

  41. Molar mass • The mass of one mole is called “molar mass” • Ex. 1 mol Li = 6.94 g Li • This is expressed as 6.94 g/mol • What are the following molar masses? S SO2 Cu3(BO3)2 32.06 g/mol 64.06 g/mol 308.1 g/mol Calculate molar masses (to 2 decimal places) CaCl2 (NH4)2CO3 O2 Pb3(PO4)2 C6H12O6 Cu x 3 = 63.5 x 3 = 190. 5 B x 2 = 10.8 x 2 = 21.6 O x 6 = 16.0 x 6 = 96.0 308.1g

  42. Learning Check! Find the molar mass (usually we round to the tenths place) • 1 mole of Br atoms • 1 mole of Sn atoms = 79.9 g/mole = 118.7 g/mole

  43. Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = 111.1 g/mol 1 mole Ca x 40.1 g/mol + 2 moles Cl x 35.5 g/mol = 111.1 g/mol CaCl2 1 mole of N2O4 = 92.0 g/mol

  44. Learning Check! • Molar Mass of K2O = ? Grams/mole B. MolarMass of antacid Al(OH)3 = ? Grams/mole

  45. Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass.

  46. Calculations with Molar Mass molar mass Grams Moles

  47. Formula gfm mass mol (n) HCl 0.25 H2SO4 53.15 NaCl 3.55 Cu 1.27 Converting between grams and moles • If we are given the # of grams of a compound we can determine the # of moles, & vise-versa • In order to convert from one to the other you must first calculate molar mass g = mol given gfm mol = g given 1 mol 1 mole gfm 36.46 9.1 98.08 0.5419 58.44 207 63.55 0.0200

  48. Converting between Grams and Moles • USE MOLAR MASS as your conversion factor!

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