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Homework Answers Page 104, Questions 1-3

Homework Answers Page 104, Questions 1-3. 24 µ 20.00g = 3.33 6.00g  argon is 3.33 times heavier than carbon. If carbon is 12 µ then argon is: 3.33 x 12µ = 40.0µ Divide each actual mass by 13.9g: Stir rod: 1.00 100 mL beaker: 3.61 250 mL flask: 5.38 Dish: 1.68 Graduate: 4.72.

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Homework Answers Page 104, Questions 1-3

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  1. Homework AnswersPage 104, Questions 1-3 • 24µ • 20.00g = 3.33 6.00g argon is 3.33 times heavier than carbon. If carbon is 12µ then argon is: 3.33 x 12µ = 40.0µ • Divide each actual mass by 13.9g:Stir rod: 1.00100 mL beaker: 3.61250 mL flask: 5.38Dish: 1.68Graduate: 4.72

  2. The Meaning of the Chemical Equation e.g.: 2 C(s) + O2(g) 2 CO(g) • two atoms of carbon must react with one molecule of oxygen to produce two molecules of carbon monoxide. • We can use any multiple of these proportions. e.g.: 4 C(s) + 2 O2(g) 4 CO(g) 200 C(s) + 100 O2(g) 200 CO(g) 2 doz C(s) + 1 doz O2(g) 2 doz CO(g) The chemist uses moles. 2 moles C(s) + 1 mole O2(g) 2 moles CO(g)

  3. The Mole • The mole is the chemist’s dozen • One mole of anything is 6.02 x 1023 of that thing e.g.: One mole of cookies is 6.02 x 1023 cookies 5 moles of atoms is 5(6.02 x 1023) = 3.01 x 1024 atoms How long would it take to count to 1 mole? (6.02 x 1023) (10s) (1min) (1h) (1d) (1y) (1century) (50 ) (60 s)(60min)(24h)(365d) (100 y) = 3.82 x 1013 centuries = 38.2 trillion centuries!!

  4. Example:What is the molar mass of: H2O H 1.008g x 2 O 16.00g Total: 18.02g Molar Mass Fe 55.8g Molar Mass Molar mass of a compound / element / molecule is the mass in grams of 1 mole of the particles that make up the substance. The molar mass is equivalent to the formula mass (amu) with units changed to grams H2O 1 mol of H2O = 18.0 g = 6.02 x 1023 molecules of H2O Fe 1 mol of Fe = 55.8 g = 6.02 x 1023 atoms of Fe

  5. Conversion Involving Moles, Atoms Molecules and Mass Example: How many wheels are there in 12 dozen bikes? (unitary rates) ? Wheels = 12 dozen bikes x 12 bikes x 2wheels 1dozen bikes 1 bike = 288 wheels Example: How many Fluorine molecules (F2) are there in 4.00 mol of fluorine gas ? Molecule F2 = 4.00 mol F2 x 6.02 x 1023 molecules F2 1 mol F2 = 2.41 x 1024 molecules F2

  6. Let’s take it one step further Example: How many atoms of F are in 4.00 mol of F2? ? atoms F = 4.00 mol F2 x 6.02 x 1023 molecules F2 x 2 atoms F 1 mol F2 1 molecule F2 =4.82 x 1024 atoms F Example: How many atoms are equal to 5.00 x 10-7 mol of Au? ? Atoms of Au = 5.00x 10-7 mol Au x 6.02 x 1023 atoms Au 1 mol Au = 3.01x 1017 atoms Au Example: What is the mass (in grams) of 1 atom of fluorine? ?g for 1 atom F = 1 atom F x 1 mol F x 19.0 g 6.02 x 1023 atoms 1 mol F = 3.16x 10-23 g

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