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More Unit conversions Convert 45.7 kg to g Convert 0.73 mL to L Convert 3.6 Ms to ns 4.57*10 4 g 730 L =7.3*10 2 L 3.6*10 15 ns answers Convert 0.001 mg.

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Presentation on theme: "More Unit conversions Convert 45.7 kg to g Convert 0.73 mL to L Convert 3.6 Ms to ns 4.57*10 4 g 730 L =7.3*10 2 L 3.6*10 15 ns answers Convert 0.001 mg."— Presentation transcript:

1 More Unit conversions Convert 45.7 kg to g Convert 0.73 mL to L Convert 3.6 Ms to ns 4.57*10 4 g 730 L =7.3*10 2 L 3.6*10 15 ns answers Convert mg to pg pg

2 Convert 7.2 kg/L to mg/ nL Hint: convert numerator first, then convert denominator and finally divide numerator result by denominator result. Answer : 7200 mg/nL

3 Convert 3*10 10 cm/kg to km/dg. A.3*10 -5 km/dg B.3*10 5 C.30 D.300 E.None of the above

4 INTRO TO MOLES: Every science involves counting…. Astronomers count …… Animal biologists count ……. Bacteriologists count …..Chemists count…….

5 Doc asks another dumb question: How long would it take the current, fastest computer in the world (The Chinese Tihane-2 as of June 2013 ) to count all the molecules of water in a teacup assuming it counted at its maximum processor rate = 34,000,000,000,000,000 molecules/second (=3400 THz=3.4*10 6 GHz 1 ) ? Answer: ~ 3.2 years 1 ~ 1 million times faster than a typical laptop

6 Student Learning Outcome 5 Students should be able to perform basic chemical calculations connected to: mole-weight-count conversions reaction stoichiometry limiting yields. Todays Student Learning Objective (SLO): Translation: How do chemists count atoms and molecules without actually having to count them ???

7 Chemists count atoms and molecules using… Moles

8 A trip to Mole land Moles connect the atomic world to human world Moles allows us to conveniently connect between these worlds using a scale ~ 30 CO 2 molecules arranged in shape of muffin man (IBM) ~ m ~ molecules in the shape of a couch potato ~2 m

9 The mole: starting definitions What is a chemical mole ? # atoms in g of 12 C *10 23 atoms (Avogadros Number) The usual textbook rant……. … Not that helpful when first starting out…

10 A better beginning: the mole concept is really … the same idea as a `dozen.

11 IN-CLASS EGG CALCULATIONS

12 EGG WORLD CHEMISTRY WORLD Smallest unit Practical Counting unit Dozen 1 egg 1 molecule Mole (The chemists dozen)

13 EGG WORLD CHEMISTRY WORLD grams/dozen (WEIGH) Practical mass unit # of smallest units in practical counting unit 1 dozen=12 1 mole *10 23 grams/mole =gram molecular weight = MW (molecular weight) (ADD) (Avogadros #) Eggs vs. chemistry world (continued)

14 THE ONE PLACE EGG WORLD AND CHEMISTRY WORLD DEVIATE A TEENY BIT: Mass dozen Egg world Chemistry world Mass = molecular weight mol(MW) Must weigh box of eggs Just add up atomic masses using Periodic Table in grams

15 Mass (grams) = MW=Molecular mol Weight = sum of masses in grams of component elements in a compound. (element masses are average masses taken from Periodic Table)

16 Example of MW Calculation: What is the MW of methane =CH 4 ?? CHCH atomic mass (Table) ~ ~1 # atoms/molecule 1414 product ~12*1=12 ~1*4 = 4 Sum = MW = 12+4=16 g/mole

17 In – class exercise on Molecular Weight (MW) calculations H 2 SO 4 CaCl 2 Cu 3 (PO 4 ) 2 2*1 + 1*32 + 4*16 = 98 g/mol 1*40 + 2*35.4 = g/mol 3* *(1*31 +4*16) = g/mol Find the MW of… CaCl 2 *2H 2 O 1*40 + 2* *(2*1 + 1*16)=146.8 g/mol 2 `waters of hydration per CaCl 2

18 IN-CLASS simple mole calculations (on board) the dozen method way

19 Another way to view mole calculations (if you are allergic to eggs): the triangle Map Method Moles (n) Weight (w) molecule count (N) ALL ROADS LEAD THROUGH MOLES

20 Moles (n) Weight (w) molecule count (N) Divide up Multiply Down The triangle `trick

21 mole math the triangle way Moles (n) Weight (w) Molecule count (N) w= n x MW If you have moles they multiply !! (because… moles breed whenever they can) N= n*6.02*10 23 You always get MW and Avogadros # = 6.02*10 23

22 reverse mole math the triangle way Moles (n) Weight (w)Molecule count (N) n = w MW If you want moles …dont let these horny critters multiply…divide them up!!! n= N 6.02*10 23

23 Trips around the triangle: N w Moles (n) Weight (w) Given molecule count N=20 w= n*MW = 20 * *10 23 n= *10 23 Given: 100 g/mol =MW Given: chemists dozen =1 mol count=6.02*10 23 ? All roads lead through moles w~3.3* g

24 Trips around the triangle: w N Moles (n) Given weight w=200 g Molecule count N n= w = 200 MW 100 N=n x 6.02*10 23 = 200 x 6.02* Given: 100 g/mol =MW Given : chemists dozen =1 mol count=6.02*10 23 ? All roads lead through moles N=1.2*10 24

25 AN ANECDOTE How do you get to the Lincoln Center for the Performing Arts ? Practice, practice, practice…. An `out-of-towner visiting NYC for the first time asks Joshua Bell (worlds greatest violinist): Joshuas answer (supposedly):

26 a)weight per mole (MW): what does a mole of C 6 H 12 O 6 weigh ? (C=12; H=1; O=16) 6* *1 + 6*16 = 180 g/mol 1.1) mole to mass: how many g C 6 H 12 O 6 of are present in mole of C 6 H 12 O 6 ? mol * 180 g/mol = 1 g 1.2) mass to mole: how many moles of C 6 H 12 O 6 are in 360 g of C 6 H 12 O 6 ? Exercise #3a: mole calculations part g/180 g mol -1 = 2 moles

27 Exercise #3a: mole calculations part 1 (continued) 1.3) mole to # molecule: how many molecules of C 6 H 12 O 6 are in 0.5 mol of C 6 H 12 O 6 ? 0.5 mol *6*10 23 molecules/mol = 3*10 23 molecules 1.4) mass to # molecules: how many molecules of C 6 H 12 O 6 are in 120 g of C 6 H 12 O 6 ? (120/180) mol * 6*10 23 molecules =4*10 23 molecules mol

28 1.5) # molecules to moles: how many moles in 3*10 24 molecules of C 6 H 12 O 6 ? 3*10 24 molecules/ 6*10 23 molecules/mol = 5 moles 1.6) # molecules to mass : How many grams of C 6 H 12 O 6 are in 2.0 *10 22 molecules of C 6 H 12 O 6 ? 2*10 22 molecules * 180 g 6*10 23 molecules/mol mol = * 180 = 6 grams Exercise 5 part 1 (continued)

29 The gram molecular mass of D form N-methylphenyl-2- propan-2-amine (the active form of crystal meth) is g/mol. How many moles of crystal meth are in a typical street `teenth = 1/16 of an ounce= 1.80 grams ? (Note: 1 mol count=6.022*10 23.) A.7.27*10 21 B C.82.9 D.2.48* E.8.98*10 25 F G.My answer isnt above

30 B1-Aflatoxin (MW=328.2 g/mol) is a naturally occurring, horribly toxic poison derived from Aspergillus fungi, a common contaminant in corn. It causes cancer in most humans at the staggeringly low exposure level of 1*10 17 molecules. What is the equivalent mass of aflatoxin represented by this count ? (Note: 1 mol count=6.022*10 23.) A.3.28* g B.1.84*10 -4 g C. 5.45*10 -5 g D.5.06* g E.1.98* g F.6.02*10 6 g G.My answer isnt above

31 Micro chip manufacture requires nearly oxygen-free conditions wherein the concentration of O 2 is at or below 17 pg/L. Given that the atomic mass of O is 16 g/mol, about how many molecules of O 2 /L does this represent ? Note: 1 mol count=6.022*10 23 A.5.4*10 24 B.3.5*10 22 C.5.3*10 22 D.3.2*10 11 E.6.4*10 12 F.1.9*10 13 G.My answer isnt above


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