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TUESDAY/Wednesday!

TUESDAY/Wednesday!. The Mole & Avogadro’s Number p.2 – converting particles/moles. Chapter 7: The Mole and Chemical Composition. Pgs. 222-257. Mole. Chemistry is a quantitative science - we need a "counting unit” for atoms and molecules. MOLE (mol )

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TUESDAY/Wednesday!

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  1. TUESDAY/Wednesday! • The Mole & Avogadro’s Number • p.2 – converting particles/moles

  2. Chapter 7:The Mole and Chemical Composition Pgs. 222-257

  3. Mole • Chemistry is a quantitative science - we need a "counting unit” for atoms and molecules. • MOLE (mol) • 1 mole of any substance is equal to as many particles as there are in 12.0 g of Carbon-12.

  4. How Big is a Mole? One mole of marbles would cover the entire Earth (oceans included) for a depth of two miles. One mole of $1 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.

  5. Amedeo Avogadro(1776 – 1856)The Amount of moles can tell us how many particles (like atoms, ions or molecules) Particles in a Mole (atoms, ions or molecules) Avagadro’s number = 6.022 x 1023 1 mole of anything = 6.022 x 1023 objects

  6. Counting Units

  7. Counting Units

  8. Avogadro’s Number:

  9. How to type that large number in your calculator! Lets try this again… • Enter 6.02 • 2nd button • EE button (an “E” will show up in the screen) • Enter 23

  10. Moles and Particles Conversion Practice: • How many particles are in .375 moles of CO2? • If there are 8.62x1019 particles in CO2, how many moles are present?

  11. Conversion Practice – p2 Packet O Fun! MUST USE CONVERSION FACTOR AND WRITE OUT UNITS FOR CREDIT!!!!!

  12. Wednesday! • Go over page 2 • Molar Mass • p3 - first column • QUIZ TOMORROW – SIMPLE CONVERSIONS AND MOLAR MASS

  13. Molar Mass • Molar Mass is the amount of grams in one mole of a substance • Units for molar mass is g/mol How do we find molar mass? • Count the atoms in the compound and use the atomic masses found on the periodic table to figure each atoms contribution 1. Li = 6.941 g/mol 2. N2H4 N = 2 x 14.01 = 28.02 + H = 4 x 1.008 = 4.03 32.05 g/mol 2. Zn3(PO4)2

  14. Practice finding molar mass of the compounds on p.3 of your Packet O Fun!

  15. Thursday • Go over molar mass p.3 • QUIZ • Simple Mole Conversions

  16. Mole Conversions: • Molar mass can be used to convert between moles of a substance and grams of a substance • Can be used as a conversion factor. • Example: • 1 mol H2 = 2.016 g H2 or 1 mole = molar mass • 2.016 g H2 • 1 mol H2 • 1 mol H2 • 2.016 g H2

  17. Converting: Moles and Grams • How many grams are in 6.3 moles of carbon dioxide? • Answer: • 277g CO2 • How many moles are in 22.78g copper? • Answer: • 0.3585 mol Cu

  18. (p.5) Volume of a Gas 1 mol = 22.4 L The volume of 1 mol of any gas at STP is 22.4 L STP (standard temp and pressure) is 0ºC and 1 atm This can be used as another conversion factor involving moles Example: 1 mol H2 or 22.4 L H2 1 mol H2 = 22.4 L H2 22.4 L H2 1 mol H2

  19. Converting:Moles and Liters • How many liters is 0.65 mol of O2 at STP? • Answer: • 14.56 L • How many moles of Kr are in 32.9L Kr at STP? • Answer: • 1.47 molKr

  20. Practice using p.6 in your Packet O Fun!

  21. Friday • Multistep Conversions

  22. Other Conversions • The conversions using moles can be used to convert from one unit to another, but you MUST go through moles. • Possibilities: • particles  grams or grams  particles • particles  liters or liters particles • grams  moles  liters OR liters  moles  grams

  23. Examples: • How many grams of carbon dioxide are in 6.35 L of carbon dioxide? • Answer • 12.5 g CO2 • How many molecules of nitrogen dioxide are in 43.6 g of nitrogen dioxide? • Answer: • 5.71 × 1023 molecules NO2

  24. P

  25. Percent Composition • The percentage by mass of each element in a compound (also known as percent by mass) • Can be calculated for any element in a compound if the formula of the compound is known

  26. Determining Percent Composition • To find the percentage by mass of each element in a compound: • Find the molar mass of each type of element • Find the total molar mass • Divide the part over the whole and multiple by 100

  27. Calculating Percent Composition • Calculate the percent composition of each element in CO2 • Answer: • Molar mass of CO2 is 44.01g/mol

  28. Calculating Percent Composition • Calculate the percent composition of each element in H2SO4 • Answer: • Molar Mass of H2SO4 is 98.09g/mol • Mass of H is 2.016g /98.09g = 2.055% H • Mass of S is 32.07g /98.09g = 32.69% S • Mass of O is 64.00g /98.09g = 65.25% O

  29. Practice % Composition on p.11 in Packet O Fun!

  30. Empirical Formula • A chemical formula that shows the composition of a compound in terms of the relative numbers and kinds of atoms in the simplest ratio • Example: • Glucose, C6H12O6, has an empirical formula of CH2O • If unable to reduce, the empirical formula can be calculated from the percent composition

  31. Determining Empirical Formula: if you can reduce, then just reduce!! Determine the empirical formula of N2O4 Answer: NO2

  32. Determining Empirical Formula: If you cannot reduce, then it is a bit more complicated… • Example 2: Determine the empirical formula of a compound that is 60.0% C, 13.4% H, and 26.6% O. 1. Find the amount in moles of each (for simplicity we assume that we have exactly 100 grams of material): 2. Determine the simplest whole-number ratio of the moles by dividing each number of moles by the smallest number of moles: • Answer: C3H8O

  33. Practicing Empirical Formula Practice determining empirical formulas on p.12-13 of your Packet O Fun.

  34. Molecular Formula A chemical formula that shows the number and kinds of atoms in a molecule, but not the arrangement of the atoms Can be determined from the empirical formula and the molar mass Generally, the molecular formula is a whole-number multiple of the empirical formula

  35. Determining Molecular Formula Determine the molecular formula of a compound that has the empirical formula C3H8O and a molecular mass of 180.28g/mol. Answer: C9H24O3

  36. Determining Molecular Formula • Determine the molecular formula of a compound that is 64.27% C, 7.19% H, 28.54% O, and has a molar mass of 168.19g/mol. • Answer: • Empirical formula = C3H4O • Molecular formula = C9H12O3

  37. Practicing Molecular Formula Practice determining molecular formula using the empirical formulas on p.12-13 of your Packet O Fun. Then complete the extra practice on p.15-16 in P of F.

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