1. Warmup: 5 minutes 1. Why do we use moles? Makes it easier to measure chemical quantities because atoms and molecules are very small. 2. Define the following ‘molecabulary’ words demoleition molearchy molectomy 3. a. What is a mole's favorite movie? b. What did Avogadro teach his students in math class? c. What kind of fruit did Avogadro eat in the summer?

2. Molar Mass Conversions and Empirical Formulas *need calculator and PT demoleition - the destruction which moles bring about in your yard. molearchy - government in which moles are in complete control; under this government Mole Day is celebrated twice a year and chemistry is the only scientific subject taught in school molectomy - the process of removing a mole's insides

3. a. What is a mole's favorite movie? b. What did Avogadro teach his students in math class? c. What kind of fruit did Avogadro eat in the summer? The Green Mole Moletiplication Watermolens

4. 1: What is the molar mass of Na 2 SO 4 ? Na: 2 mole x 22.99 = 45.98 S: 1 mole x 32.07 = 32.07 O: 4 mole x 16.00 = 64.00 = 142.05 g/mole Calculating Molar Mass 1) Find the atomic mass of each element 2) Multiply the number of moles times the atomic mass of for each element 3) Add values, round to the hundredths place, and report your answer in g/mole

5. 2. Calculate the molar masses of the following compounds: a. Zr(SeO 3 ) 2 b. NH 4 OH c. Ca 2 Fe(CN) 6. 12H 2 0 14.01 + 1.01(5) + 16.00 35.06 g/mole 91.22 + 78.96(2) + 16.00(6) 345.14 g/mole 40.08(2) + 55.85 + 12.01(6) + 14.01(6) + 1.01(24) + 16.00(12) 508.37 g/mole

6. Ex 3: What is the molar mass of Pb(NO 3 ) 2 ? Pb: 1 mole x 207.20 = 207.20 N: 2 mole x 14.01 = 28.02 O: 6 mole x 16.00 = 96.00 = 331.22 g/mole Ex 4: Find the mass % of each element in Pb(NO 3 ) 2 Pb 207.20 g/mole 331.22 g/mole = 0.6256 or 62.56% N 28.02 g/mole 331.22 g/mole = 0.0846 or 8.46% O 96.00 g/mole 331.22 g/mole = 0.2898 or 28.98%

7. 2 5. What are the mass percents of iron and oxygen in Fe 2 O 3 ? Iron: (2 x 55.85 g/mole) x 100= 69.94 % (159.7 g/mole) Oxygen: (3 x 16.00 g/mole) x 100 = 30.06 % (159.7 g/mole)

8. Conversions using Molar Mass Ex 6: How many moles is 5.69 grams of CH 4 ? 5.69 g CH 4 ( ) = ( ) 1 mole CH 4 16.05 g CH 4 0.355 mole CH 4

9. Ex 7: How many moles is 4.56 g of CO 2 ? 4.56 g CO 2 ( ) = ( ) You need the molar mass of carbon dioxide 1 mole CO 2 44.01 g CO 2 0.104 mole CO 2

10. Ex 8: Find the mass (in grams) of 9.8 moles of lithium fluoride 9.8 mole LiF ( ) = ( ) You need the formula and molar mass of this compound FIRST! 25.94g LiF 1 mole LiF 250 g LiF

11. Empirical formula: shows the relative numbers of atoms of each element using the smallest whole numbers. Molecular formula: tells us actual numbers of atoms of each element in the molecule. They CAN BE the same. CH 2 O Formaldehyde! Emp. formula for lots of organic molecules, ex. C 6 H 12 O 6 C3H4O3C3H4O3 Does not exist; emp. formula for ascorbic acid: C 6 H 8 O 6 Molar mass must be known.

12. 9. The empirical formula of styrene is CH; its formula weight (‘molar mass’) is 104.1 g/mole. What is the molecular formula of styrene? molecular formula = multiple of the empirical formula * molar mass of the compound is needed Molar mass styrene = 104.1 g/mole Molar mass emp.form. = 13.02 g/mole = 7.995391… = 8 molecular formula = C 8 H 8

13. 10. A 25.0 gram sample of a compound contains 6.64 grams potassium, 8.84 g chromium, 9.52g oxygen. Find the empirical formula of this compound. Step 1: Convert each mass to moles 0.170 mole K 0.170 mole Cr 0.595 mole O 0.170 0.170 0.170 Step 2. Get ratio of moles (by dividing each # moles by smallest # moles) Mole ratio: 1 mole K: 1 mole Cr: 3.50 moles O Step 3: If the numbers in the ratio are not integers, double, triple, etc each number until they are all integers….you may want to round slightly (ex. 2.98 can be 3 but 2.49 should be doubled to 4.98, then rounded to 5) New ratio: 2 : 2 : 7 K 2 Cr 2 O 7, potassium dichromate

14. 11. Phenol is a compound which contains 76.57% carbon, 6.43% hydrogen, and 17.0% oxygen. What is the empirical formula of phenol? If you are given percents of elements instead of actual masses, turn each percent into a gram amount out of a 100g sample Step 1: Convert each mass to moles 76.57g C/12.01 g C6.43 g H/1.01g H17.0 g O/16.00 g O 6.376 mole C 6.366 mole H 1.06 mole O 1.06 1.06 1.06 Step 2. Get ratio of moles (by dividing each # moles by smallest # moles) Mole ratio: 6 mole C: 6 mole H: 1 moles O C 6 H 6 O = phenol!

15. 12. A 5.00 gram sample of an acid contains 2.00 g carbon, 0.336 g hydrogen, and 2.66 g oxygen. Find the molecular formula of this acid and give the proper name if its molar mass = 60.06 g/mole Try this yourself. It is acetic acid. We will do the work on the board in a bit for 12 and 13. 13. Monosodium glutamate (MSG), a food flavor enhancer, has been blamed for "Chinese restaurant syndrome", the symptoms of which are headaches and chest pains MSG has the following composition by mass: 35.51% carbon4.77 % hydrogen 37.85 % oxygen 8.29 % nitrogen 13.60 % sodium What is its molecular formula it its molar mass is 169 g?