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The Mole We use a package for atoms and molecules called a mole A mole =

The Mole We use a package for atoms and molecules called a mole A mole = a. the number of Carbon atoms in 12 g of 12 C 6.022 x 10 23 units = Avogadro’s Number The amount of an element equal to its atomic mass 1 mole of natural C atoms weighs 12.01 g and has 6.022 x 10 23 atoms

jedidiah-braylon
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The Mole We use a package for atoms and molecules called a mole A mole =

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  1. The Mole • We use a package for atoms and molecules called a mole • A mole = • a. the number of Carbon atoms in 12 g of 12C • 6.022 x 1023 units = Avogadro’s Number • The amount of an element equal to its atomic mass • 1 mole of natural C atoms weighs 12.01 g and has 6.022 x 1023 atoms • 1 mole of He atoms weighs 4.003 g and has 6.022 x 1023 atoms • 1 mole of Al atoms weighs 26.98 g and has 6.022 x 1023 atoms • Example: What is the mass of 6 Americium atoms? • Calculating moles, mass, and atoms • 1. Example: # atom / moles in 10g Al Cu I2 Hg Al Fe S

  2. C. A mole is the chemists “dozen” • A dozen marbles and a dozen peas both have 12 • A dozen marbles might weigh 100 grams • A dozen peas might weigh only 15 grams • 4. Example: 5.68 mg Si = ? atoms Si

  3. Empirical Formula = smallest whole number ratio of elements in the formula • I. Today’s Reaction • xZn(s) + yHCl(aq) --------> ZnxCly(aq) + H2(g) • Measured Mass excess Measured Mass • Safety • 6 M HCl can burn skin or put holes in clothes; wash off with water • H2(g) is flammable; do the reaction in the hood. • Use hot plate to boil off the extra water from the reaction • White fumes coming off dry solid is gaseous ZnxCly • Calculations (example) • 1.013g ZnxCly solid - 0.800g Zn(s) = 0.213g Cl in the compound • Change the mass of Zn and Cl to moles • Divide by the smallest number of moles; then round or multiply to whole #’s

  4. IV. Hints for determining empirical and molecular formulas • Convert mass % to grams of the element in 100 total grams of sample • Determine the Empirical Formula of an unknown if its Percent Composition is 47% Carbon, 47% Oxygen and 6.0% Hydrogen • Change these masses to moles by using the atomic mass of each element • Divide each number of moles by the smallest to get a small # ratio • Round off to a whole # if molar #’s are close to that whole number • Multiply the whole ratio by a factor to get all numbers to whole numbers • Multiply empirical formula by factor needed to give the correct molar mass • Molar Mass of unknown = 204.2 g/mol but C4H6O3 = 102.09 g/mol • Correct Molecular Formula: C4H6O3 x 2 = C8H12O6

  5. Incident: Mixing Acid with Water • Incident: Unrecognized Fume Hood Failure

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