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Warmup : 5 minutes

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?

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Warmup : 5 minutes

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  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 demoleitionmolearchymolectomy 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. The Green Mole Moletiplication Watermolens 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?

  4. 1: What is the molar mass of Na2SO4? Na: 2 mole x 22.99 = 45.98 S: 1 mole x 32.07 = 32.07 O: 4 mole x16.00 =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(SeO3)2 b. NH4OH c. Ca2Fe(CN)6.12H20 40.08(2) + 55.85 + 12.01(6) + 14.01(6) + 1.01(24) + 16.00(12) 508.37 g/mole 91.22 + 78.96(2) + 16.00(6) 345.14 g/mole 14.01 + 1.01(5) + 16.00 35.06 g/mole

  6. Ex 3: What is the molar mass of Pb(NO3)2? Pb: 1 mole x 207.20 = 207.20 N: 2 mole x 14.01 = 28.02 O: 6 mole x16.00 =96.00 = 331.22 g/mole Ex 4: Find the mass % of each element in Pb(NO3)2 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% Pb 207.20 g/mole 331.22 g/mole = 0.6256 or 62.56%

  7. 5. What are the mass percents of iron and oxygen in Fe2O3? 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. 1 mole CH4 0.355 mole CH4 Conversions using Molar Mass Ex 6: How many moles is 5.69 grams of CH4 ? 5.69 g CH4 ( )= ( ) 16.05 g CH4

  9. 4.56 g CO2 ( )= ( ) You need the molar mass of carbon dioxide 1 mole CO2 0.104 mole CO2 Ex 7: How many moles is 4.56 g of CO2 ? 44.01 g CO2

  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! 25.94 g LiF 250g LiF mole LiF 1

  11. CH2O Formaldehyde! Emp. formula for lots of organic molecules, ex. C6H12O6 C3H4O3 Does not exist; emp. formula for ascorbic acid: C6H8O6 Molar mass must be known. 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.

  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 = C8H8

  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 K0.170 mole Cr0.595 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 K2Cr2O7, 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 C 6.43 g H/1.01g H 17.0 g O/16.00 g O 6.376 mole C6.366 mole H1.06 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 C6H6O = 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% carbon 4.77 % hydrogen 37.85 % oxygen 8.29 % nitrogen 13.60 % sodium What is its molecular formula it its molar mass is 169 g?

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