Chapter 3 Notes

# Chapter 3 Notes - Chapter 3 Stoichiometry Lecture Outline...

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Slide No. 1 Chapter 3: Stoichiometry ± Chemical Amounts ² the mole and Avogadro’s number ² elemental analysis ± Writing and Balancing Chemical Reactions ± Reaction Stoichiometry ² reactant and product quantities ² limiting reagents and percent yield ± Solutions ² molarity ² dilutions and reactions ± Reading: All of Chapter 3 ± Homework Problems: 12(13), 18(19a), 23(24), 35(36a,d), 37(38b), 39(40), 44(111), 53(54a,b), 55(56b), 65(66), 73(74), 81(82), 94(95a,b), 96(97a,c), 100(101) Lecture Outline Slide No. 2 Counting Small Things ± How many gumballs? ² Weigh a few – get an average ² Weigh the whole sample ² Divide ± Molecules are small ² Really small ² But they all weigh the same! ± Everyday quantity measurements ² Volume: cup of sugar, gallon of milk ² Mass: pound of nails ² Number: dozen donuts ± Chemists prefer ² Mass ² Volume 3.1 The mole

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Slide No. 3 Counting Small Things ± Describe the atom in one word: ________ _______ ± Chemical Formula shows number ratio of elements: ² CO 2 N 2 H 2 ON a C l ± atomic/molecular weights show average mass ² H 2 O = 18.02 amu ± We can’t count individual atoms nor weigh individual atoms. We measure macroscopic properties--need to scale-up! ² How do you measure flour or sugar in the kitchen? ± Stoichiometry means dealing with measurable quantities (grams) while thinking about chemical reactions that occur among individual atoms and molecules. mass mole number 3.1 The mole Slide No. 4 Microscopic vs Macroscopic Masses ± Microscopic Scale ² One 12 C atom is assigned the mass of exactly 12 amu. ² All other elemental isotopes assigned relative to 12 C. ² Atomic or formula mas s = mass of one atom (element) or 1 formula unit (compound) of a substance (units = amu / unit) • He = 4.003 amu / atom •H 2 = 2.02 amu / molecule • NaOH = 40.00 amu / formula unit ± Macroscopic Scale ² Prefer to use grams (not amu) ² One mole of 12 C atoms has a mass of exactly 12 g. ² Molar mass = mass of one mole of a substance (units = g/mol). • He = 4.003 g / mol 2 = 2.02 g / mol • NaOH = 40.00 g / mol ± 1 mole = 6.02x10 23 entities = Avogadro's Number (N A ) Memorize 3.1 The mole
Slide No. 5 Avogadro's Number is Big ± How much is a mole ? ² How wealthy would the average person be if there was a mole of pennies on Planet Earth? 6.02 x 10 23 pennies 6 x 10 9 people = 1 x 10 14 pennies or \$100 trillion per person ± How heavy is a mole ? ² How heavy would all those pennies be? • 6.02 x 10 23 pennies x 2.5 g per penny = 1.5 x 10 24 g • mass of the moon = 7.36 × 10 25 g ± Biology's mole ² total length 14-19 cm ² weight 50-100 g ² burrowing pest 3.1 The mole Slide No. 6 The Mole and Chemical Formulas ± Adapted from Silberberg, Table 3.2 ± Glucose = C 6 H 12 O 6 ± MW = 180.16 amu/molecule or Molar mass = 180.16 g/mol CHO one molecule glucose (C 6 H 12 O 6 ) contains 6 atoms 12 atoms 6 atoms 6 C(12.01amu/C) = 72.06 amu 12 H(1.008 amu/H) = 12.10 amu 6 O(16.00 amu/O) = 96.00 amu one mole glucose contains 6 moles atoms 12 moles atoms 6 moles atoms 6 mol (12.01g/mol) = 72.06 g C 12 mol (1.008 g/mol) = 12.10 g H 6 mol (16.00 g/mol) = 96.00 g O 6(6.02x10 23 atoms) 12 (6.02x10 23 atoms) 6 (6.02x10 23 atoms) mass % 40.00% 6.72% 53.28% 3.1 The mole

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Slide No. 7 Working with Mole Concepts ± True of False?
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## This note was uploaded on 03/31/2008 for the course CHEM 1035 taught by Professor Jgdillard during the Fall '07 term at Virginia Tech.

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Chapter 3 Notes - Chapter 3 Stoichiometry Lecture Outline...

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