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The Mole

The Mole. 6.02 X 10 23. 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 23 (in scientific notation)

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The Mole

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  1. The Mole 6.02 X 1023

  2. 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 1023 (in scientific notation) • This number is named in honor of Amedeo 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

  3. 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.

  4. Everybody Has Avogadro’s Number!But Where Did it Come From? • 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

  5. Learning Check Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects. 1. How many paper clips in 1 rapp? a) 1 b) 4 c) 8 2. How many oranges in 2.0 rapp? a) 4 b) 8 c) 16 3. How many rapps contain 40 gummy bears? a) 5 b) 10 c) 20

  6. Molar Mass • The molar mass is the mass of one mole of a substance. • These are listed on your Periodic chart. • Examples; • Na = 22.98977 g/mole • H = 1.00794 g/mole • O = 15.9994 g/mole • U= 238.029 g/mole usually we round to the tenths place

  7. Molar Mass • What is the molar mass of C? • C = 12.011 g/mole • What is the molar mass of H20? • H = 2 x 1.00794 g/mole • O = 15.9994 g/mole • 18.0153 g/mole

  8. Molar Mass • What is the molar mass of calcium nitrate? • Ca(NO3)2 • Ca = 40.078 g/mole • N = 2 x 14.0067 g/mole • O = 6 x 15.9994 g/mole • 164.088 g/mole

  9. Other Names 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. (This is the beauty of Avogadro’s Number!) • 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 termswhich mean the SAME NUMBER… just different units

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

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

  12. The Mole • 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 Note that the NUMBER is always the same, but the MASS is very different! Mole is abbreviated mol (gee, that’s a lot quicker to write, huh?)

  13. A Mole of ParticlesContains 6.02 x 1023 particles 1 mole C 1 mole H2O 1 mole NaCl = 6.02 x 1023 C atoms = 6.02 x 1023H2O molecules = 6.02 x 1023NaCl “molecules” (technically, ionics are compounds not molecules so they are called formula units) 6.02 x 1023 Na+ ions and 6.02 x 1023Cl– ions

  14. Ways to use the mole. • We now have two mole relationships. • 6.02X1023 = 1 mole • The molar mass = 1 mole • These are both unitary rates and can be expressed as fractions. • Using water as an example; Unitary rates can be inverted when needed

  15. Avogadro’s Number as Conversion Factor 6.02 x 1023 particles 1 mole or 1 mole 6.02 x 1023 particles Note that a particle could be an atom OR a molecule!

  16. Converting Moles and Grams Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al

  17. 1. Molar mass of Al 1 mole Al = 27.0 g Al 2. Conversion factors for Al 27.0g Al or 1 mol Al 1 mol Al 27.0 g Al 3. Setup3.00 moles Al x 27.0 g Al 1 mole Al Answer = 81.0 g Al

  18. Given over one Molar Mass How many moles are in 20.00 grams of H2O ? To find the molar mass of water 2 H = 2 x 1.00794 g/mole+1 O = 1 x 15.9994 g/mol 18.01528 g/mol H2O

  19. Given over one Definition of Mole How many molecules of water would this be? Why are there four sig figs?

  20. How many hydrogen atoms are in 3.66 moles of water?

  21. How many oxygen atoms are in 55.785g of sodium phosphate?

  22. 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 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

  23. Learning Check! The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

  24. Atoms/Molecules and Grams • Since 6.02 X 1023 particles = 1 mole AND1 mole = molar mass (grams) • You can convert atoms/molecules to moles and then moles to grams! (Two step process) • You can’t go directly from atoms to grams!!!! You MUST go thru MOLES. • That’s like asking 2 dozen cookies weigh how many ounces if 1 cookie weighs 4 oz? You have to convert to dozen first!

  25. Calculations with Molar Mass molar mass Grams Moles

  26. Calculations molar mass Avogadro’s numberGrams Moles particles Everything must go through Moles!!!

  27. atoms ions molecules Grams moles 23 Molar mass 6.02x10

  28. Convert 150.35 grams of C2H5OH to Molecules Find molar mass of C2H5OH 2 Carbon 2 x 12.011 g/mol = 24.022 g 6 Hydrogen 6 x 1.00795 g/mol = 6.0477 g 1 Oxygen 1 x 15.9994 g/mol = 15.9994 g Molar mass = 46.0691 g/mol

  29. continued

  30. Convert3.0 x 1023 molecules of C6H12O6 to moles

  31. 3.0 moles of CO2 to grams • First find molar mass of CO2 1 carbon = 1 x 12.011 g/mol = 12.011 g 2 oxygen =2 x 15.9994 g/mol = 31.9988 g 44.0098 g/mol • 3.0 moles CO2 x 44.0098 g = 130g CO2 1 1 mole

  32. Atoms/Molecules and Grams How many atoms of Cu are present in 35.4 g of Cu? 35.4 g Cu 1 mol Cu 6.02 X 1023 atoms Cu 63.5 g Cu 1 mol Cu = 3.4 X 1023 atoms Cu

  33. Learning Check! How many atoms of K are present in 78.4 g of K?

  34. Learning Check! What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)?

  35. Learning Check! How many atoms of O are present in 78.1 g of oxygen? 78.1 g O2 1 mol O2 6.02 X 1023molecules O2 2 atoms O 32.0 g O2 1 mol O2 1 molecule O2

  36. Percent composition from mass • Add total mass of all elements given • Divide mass of element by total X 100 • Repeat for all elements • Total percents to check for 100% total

  37. Percent composition from formula • Find atomic mass of each element • Find molar mass by multiplying subscripts times atomic mass and totaling • To find percent composition of each element, multiply subscript times atomic mass and divide by molar mass. Part X 100 = % Whole

  38. Ex. 1 What is the percent composition of the elements in H2O? • Hydrogen has an atomic mass of 1.00794 g/mole • Oxygen has an atomic mass of 15.9994 g/mole • molar mass= 2 x 1.00794g/mole = 2.01588grams + 1 x 15.9994g/mole = 15.9994grams 18.0153g/mole

  39. Step 2 Use molar mass to find percent of each element • % Hydrogen = 2mole x 1.00794 g= 11.1 % 18.0153 g/mole • % Oxygen = 1mole x 15.9994 g = 88.8 % 18.0153 g/mole Total 11.1 + 88.8  100 %

  40. Na 22.98977 g/mol Cl 35.4527 g/mol NaCl 58.4425 g/mol % of Na 22.98977 g/mol x 100 = 39.3 % 58.4425 g/mol % of Cl 35.4527 g/mol x 100 = 60.7 % 58.4425 g/mol 39.3% + 60.7% = 100 % What is the percent composition of NaCl?

  41. Percent Composition What is the percent carbon in C5H8NO4 (the glutamic acid used to make MSG monosodium glutamate), a compound used to flavor foods and tenderize meats? a) 8.22 %C b) 24.3 %C c) 41.1 %C

  42. Empirical Formula The empirical formula of a compound is the smallest whole number ratio of the number of atoms of each element in the substance.

  43. Empirical Formula • The empirical formula can be found experimentally. • The actual formula can be determined after the empirical formula is discovered • Examples • Dinitrogen tetrahydride • N2H4 • Has an empirical formula of NH2 • Examples • Hydrogen peroxide • H2O2 • Has an empirical formula of HO

  44. Steps for finding empirical formula • Turn all given quantities into moles. • Divide the larger number of moles by the smallest number of moles. • Round to the tenths decimal place. • Multiply by whole numbers to remove decimal values. {If whole numbers are not obtained (in step 3), multiply through by the smallest number that will give all whole numbers} • Express the ratio as a chemical formula.

  45. A sample of a brown gas, a major air pollutant, is found to contain 2.34 g N and 5.34g O. Determine a formula for this substance. require mole ratios so convert grams to moles moles of N = 2.34g of N = 0.167 moles of N 14.01 g/mole moles of O = 5.34 g = 0.334 moles of O 16.00 g/mole Formula:

  46. 1.4429614 mole S= 1.5 S 0.9621273 mole Fe Fe FeS1.5x 2 = Fe2S3 What is the empirical formula of a compound which contains 53.73g of Fe and 46.27g of S? Fe =0.9621273 mole Fe S =1.4429614 mole S

  47. 1.587662 mole Na= 2.0 Na 0.7921162 mole S S 2.381339 mole O= 3.0 O 0.7921162 mole S S Na2SO3 What is the empirical formula for sodium sulfite if it contains 36.5g sodium, 25.4 g sulfur and 38.1 g oxygen? Na =1.587662 mole Na S =0.7921162 mole S O =2.381339 mole O

  48. 11.01256027 mole H = 2 H 5.5564836719 mole O O H2O What is the formula of a compound with 11.1 % Hydrogen and 88.9 % Oxygen? H = 11.0125602714 moles H O = 5.5564836719 mole O

  49. Molecular Formula The molecular formula is the actual ratio of atoms in a compound.

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