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# “ Practice, practice, practice….”

`Body Parts’ Mole calculations (continued). “ Practice, practice, practice….”. In-class exercise #3b : chem 1114 Mole Calculations: part 2. 3 .1)mole to mole: how many moles of O are present in 0.1666 mole of C 6 H 12 O 6 ?. 1 mol O. 3 .2 ) mole to mole

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## “ Practice, practice, practice….”

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1. `Body Parts’ Mole calculations (continued) “Practice, practice, practice….”

2. In-class exercise #3b: chem1114 MoleCalculations: part 2 3.1)mole to mole: how many moles of O are present in 0.1666 mole of C6 H12O6? 1 mol O 3.2) mole to mole how many moles of C6H12O6 can be made with 12 mole of O ? 2moles C6H12O6

3. In-class exercise #7b: chem 1114 Mole Calculations: part 2 3.3) weight to moles how many moles of C6H12O6 in a sample containing 216 g C ? 3mol 3.4)moles to weight how many grams of C6H12O6 are formed with 0.2666 mol H? = 4 g

4. 3.5) moles to molecules how many molecules of O are present in 0.1388 mol of C6 H12O6? =5*1023 3.6) molecules to moles how many moles of C6 H12O6 are formed from 4.35*1025atoms of H ? 6moles

5. 3.7 mass to molecules: how many moleculesof C6 H12O6form from 84 g of C ? 7*1023 molecules ofC6H12O6 3.8 atoms to mass: how many grams of H are combined with 2.4*1024 atoms of O in C6H12O 6 ? 8grams H

6. The road trip through mole land so far… • Basic mole-mass-count conversions (Bermuda triangle: divide up, multiply down) • Mole ratio conversion within a compound (`body parts’ relationships)

7. The mole road ahead…. • % composition problems and combustion analysis (pp. 384-392) • Reaction balancing (pp. 392-395) • Reaction stoichiometry predictions, limiting yields and % yields ( pp. 396-406)

8. % composition problems: using mole concept to convert weights to formulas Sample % composition problem #1 A compound of N and O contains 63.63 wt % N and 36.36 wt % O. What is the empiric formula of the compound ?

9. Definition: empiric formula= mole ratio of elements in a compound expressed inlowestwhole numbers Example: CH2O = empiric formula of glucose (sugar we metabolize) Actual molecular formula (what it really has in atom count) C6H12O6= (CH2O)6 Sugar =Carbo hydrate

10. Which formulas below are empiric (= lowest common denominator form) ?? Now EMPIRIC ÷ 3 NOT EMPIRIC C3H6O3 CH2O EMPIRIC…3 & 7 have no shared factors N3F7 H3P9O12S5 Do not write HP3O4S5/3

11. % composition Problem 1: empiric formula determination A compound of N and O contains 63.63% N and 36.36 %O. What is the empiric formula of the compound? let’s do it on the board…

12. Sample problem #1; SUMMARIZED =Laughing gas OFFICIAL NAME… =>N2O Dinitrogen monoxide n nmin AW=Atomic wt (g/mol) n=w/AW moles w(g) 4.545 = 2 2.273 63.63/14= 4.545 63.63 14 36.36/16= 2.273 2.273 =1 2.273 36.36 16

13. An oxide of nitrogen contains 46.7 wt. % N and 53.3 % O. What is it’s empiric formula ? (problem 35, page 417) • NO3 • NO2 • N2O • N3O7 • NO • None of the above

14. % composition Problem 2: empiric formula determination with a twist A compound composed of C,H and O is 48.64% C and 8.16 % H and 43.2 % O by mass. What is the empiric formula ? Answer: C1.5H3O1 C3H6O2 x FACTOR 1.5*2= 3 48.64/12= 4.05 4.05/2.7= 1.5 ? 8.16/1= 8.16 3.0*2= 6 8.16/2.7= 3.0 43.2/16= 2.70 2.7/2.7= 1 1*2= 3

15. A compound contains:0.3158 g C, 0.0526 g H and 0.631 g O. What is its empiric formula ? • C2H4O3 • C4H2O3 • CHO • CH2O • None of the above

16. % composition Problem 3: empiric + molecular formula determination The previous empiric compound (C2H4O3) has a molecular weight of 228 g/mol. What is the molecular formula of the compound ? Let’s do this on the board…

17. A compound with the empiric formula CH2O has a molecular weight of 180 g/mol. Given C=12 g/mol, H=1 g/mol and O=16 g/mol what is the molecular formula for the compound ? • CH2O • C3H6O3 • C6H12O6 • C12H24O12 • None of the above

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