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Chapter 10

Chapter 10. The Mole. 10.1 Measuring Matter. Dozen eggs Pair of gloves. The mole. SI unit, measures the amount of substance 602,213,670,000,000,000,000,000 A mole of pennies would be $6,022,136,700,000,000,000,000

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Chapter 10

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  1. Chapter 10 The Mole

  2. 10.1 Measuring Matter • Dozen eggs • Pair of gloves

  3. The mole • SI unit, measures the amount of substance • 602,213,670,000,000,000,000,000 • A mole of pennies would be $6,022,136,700,000,000,000,000 • six sextillion, twenty-two quintillion, one hundred thirty-six quadrillion, seven hundred trillion dollars • 6.02 x 1023 particles of matter

  4. 6.02 x 1023 =Avogadro’s number • The number of representative particles in one mole of a pure substance • Representative particle = • Formula unit (ionic compounds) • Molecule (covalent compounds) • Atom

  5. One mole of Fe = 6.02 x 1023 atoms H2O = 6.02 x 1023 molecules CaCl2 = 6.02 x 1023 formula units

  6. Moles Representative particles • Conversion factor = • 6.02 x 1023 particles 1 mole How many atoms are in 2.00 mol of argon?

  7. How many molecules are in 7.25 mol of carbon dioxide? Challenge: How many oxygen atoms are in 5.0 moles of oxygen molecules? (Oxygen is diatomic)

  8. Representative particles Moles How many moles are in 1.62 x 1023 atoms of argon? How many moles are in 4.35 x 1024 molecules of dinitrogen triflouride?

  9. 10.2 Mass and the Mole • Molar mass = the mass in grams of one mole of a pure substance (atom, molecule, formula unit) • Equal to atomic mass (on periodic table) • Unit = g/mol

  10. Mass of atoms is found on the periodic table • K = • Mass of compounds must be calculated • H20 • CO2

  11. Calculating molar mass • What is the molar mass of barium acetate? • What is the molar mass of ammonium sulfate?

  12. Mass Moles How many moles are in 12.5 g of Carbon dioxide? How many moles are in 83.2 g of H2SO4?

  13. Moles Mass • What is the mass in grams of 1.5 mol of sodium chloride? • What is the mass in grams of 0.774 mol of oxygen?

  14. Converting between units Must ALWAYS go to moles first

  15. How many atoms are in a 44.3 g piece of iron?

  16. What is the mass in grams of 2.3 x 1022 formula units of sodium phosphate?

  17. How many aluminum ions are present in 35.6 g AlCl3? • How many chlorine ions are present in 35.6 g AlCl3?

  18. 10.4 Empirical and Molecular Formulas • Empirical formula – shows the smallest whole-number ration of atoms in a compound • Molecular formula – gives the actual number of each kind of atom in a molecule • C6H12O6

  19. Percent Composition • The percent by mass of each element in a compound • The percents of all the elements should add up to 100

  20. Calculating % Composition • Find the total molar mass of each element in the compound. • Find the molar mass of the entire compound. • Divide the total molar mass of each element by the molar mass of the compound then multiply by 100 • Check that all your percentages add up to 100

  21. % composition of C3F6 • Total mass of C = total mass of F = • Mass of compound C3F6 = • % of C = % of F = • Check your work!

  22. What is the percent composition of phosphoric acid?

  23. Empirical Formula • The formula with the smallest whole number ratio of elements in a compound

  24. Calculating Empirical Formulas • Change % to g (assume 100 g of compound so 30% = 30 g) • Convert each element from g to moles • Divide each mole amount by the smallest number from step 2 • Change to a whole number = subscript in empirical formula

  25. What is the empirical formula for a compound that is 48.64% Carbon, 8.16% Hydrogen, and 43.20% Oxygen?

  26. What is the empirical formula of a compound that is 43.7% P and 56.3% O?

  27. Molecular Formula • To find the molecular formula you must know • Empirical formula • Molar mass of compound • Can be the same as the empirical formula but often is not

  28. Calculating Molecular Formula • Calculate the mass of the empirical formula • Divide molar mass of compound (will be given) by mass of empirical formula • Multiply each subscript in the empirical formula by the answer from step 2

  29. A compound who’s empirical formula is NO2 has a molar mass of 92 g/mol. What is the compound’s molecular formula?

  30. An unknown compound contains 58.5% carbon, 9.8% hydrogen, and 31.4% oxygen. Its molar mass is 102 g/mol. What are its empirical and molecular formulas?

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