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

e.g.:2 C (s) + O 2(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 O 2(g)  4 CO (g) 200 C (s) O 2(g)  200 CO (g) 2 doz C (s) + 1 doz O 2(g)  2 doz CO (g) The chemist uses moles. 2 moles C (s) + 1 mole O 2(g)  2 moles CO (g)

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

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 1.008g x 2H 16.00gO Total: 18.02g Molar Mass 1 mol of H 2 O = 18.0 g = 6.02 x molecules of H 2 O Fe 55.8gFe 1 mol of Fe = 55.8 g = 6.02 x atoms of Fe Example: What is the molar mass of: H2OH2O H2OH2O

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 bikes1 bike = 288 wheels Example: How many Fluorine molecules (F 2 ) are there in 4.00 mol of fluorine gas ? Molecule F 2 = 4.00 mol F 2 x 6.02 x molecules F 2 1 mol F 2 = 2.41 x molecules F 2

Let’s take it one step further Example: How many atoms of F are in 4.00 mol of F 2 ? Example: How many atoms are equal to 5.00 x mol of Au? ? Atoms of Au = 5.00x mol Au x 6.02 x atoms Au 1 mol Au = 3.01x atoms Au ? atoms F = 4.00 mol F 2 x 6.02 x molecules F 2 x 2 atoms F 1 mol F 2 1 molecule F 2 =4.82 x atoms F 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 atoms 1 mol F = 3.16x g