A compound will have the same composition by mass.

1. A compound will have the same composition by mass.

2. Calculate the following percentage by mass: percent = portion/total x 100 If two samples are the same substance, they should have the same percent composition by mass.

3. A compound will have the same physical and chemical characteristics.

4. Do the have the same percent composition? Are they the same compound?

6. Mass Ratio Percent Composition of compounds was used to determine the MASS RATIO between elements. Regardless of number of atoms, the MASS RATIO is the same.

7. carbon-12 The standard for mass was arbitrarily chosen to be one atom of carbon-12 the MASS RATIO between elements was then used to calculate others. The mass of one carbon-12 atom was set at 12 (exactly) “amu”. “amu” is an arbitrarily chosen amount.

8. ATOMIC MASS UNIT “amu” is an arbitrarily chosen amount. It is so small, it is not practical for actual use….. A person named Avogardo, invented a multiple that would allow the MASS RATIO to be preserved but to be measured in grams. He called it : a mole P310-317

9. The Mole A mole of any element is defined to be the same number of atoms of that element equal to the number of atoms in 12.0 g of carbon-12 P310-317

10. Molar Mass The mass of 1 mole (in grams) • Equal to the numerical value of the average atomic mass (get from periodic table) 1 mole of C atoms = 12.01 g 1 mole of Mg atoms = 24.31 g 1 mole of Cu atoms = 63.55 g Where are these numbers from? PERIODIC TABLE

11. Other Names Related to Molar Mass • Atomic Mass Single atom, mass is measured in amu’s instead of grams. Only the units are different: Atomic/Individual/MICROSCOPIC = amu Molar/A lot of/VISIBLE/MACROSCOPIC = g

12. Learning Check! Find the molar mass (usually we round to the hundreds place) = 79.90 g/mole 1 mole of Br atoms 1 mole of Sn atoms = 118.71 g/mole

13. Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of CaCl2 = 110.98 g/mol (1 mole Ca x 40.08 g/mol ) + (2 moles Cl x 35.45 g/mol) = 110.98 g/mol CaCl2

14. Molar Mass of Molecules and Compounds Mass in grams of 1 mole equal numerically to the sum of the atomic masses 1 mole of N2O4 = 92.02 g/mol

15. Learning Check! • Molar Mass of K2O = B. MolarMass of antacid Al(OH)3 = K2O = 94.20 g/mol Al(OH)3 = 78.03 g/mol

16. Other Names Related to Molar Mass • Molecular Mass/Molecular Weight: Single molecule, mass is measured in amu’s instead of grams. same numerical value as 1 mole of molecules. Only the units are different: Individual/MICROSCOPIC= amu A lot of/VISIBLE/MACROSCOPIC= g

17. Other Names Related to Molar Mass • Molecular Mass/Molecular Weight: Single molecule, mass is measured in amu’s instead of grams. But, the molecular mass/weight is the same numerical value as 1 mole of molecules. Only the units are different • Formula Mass/Formula Weight: Same goes for compounds. But again, the numerical value is the same. Only the units are different.

18. Other Names Related to Molar Mass • THE POINT: You may hear all of these termswhich mean the SAME NUMBER… just different units • Molar Mass = Gram Formula Weight in our textbook • With Avogadro’s #, you may also hear the terms: molecules, atoms, formula units, ions, particles, “things” IT DEPENDS ON WHAT YOU’RE TALKING ABOUT: example: 1 dozen eggs versus 1 dozen roses 1 mole of H2O molecules vs. 1 mole of NaCl formula units

19. Learning Check Prozac, C17H18F3NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. 309.38 grams

20. Calculations with Molar Mass molar mass Grams Moles Do you multiply or divide by molar mass? It depends on which way you’re going. Use conversion factors.

21. Converting Moles and Grams Aluminum is often used for the structure of light-weight bicycle frames. How many grams of Al are in 3.00 moles of Al? 3.00 moles Al ? g Al

22. Molar mass of 1 mole Al = 26.98 g Al 2. Conversion factors for Al 26.98 g Al or 1 mol Al 1 mol Al 26.98g Al 3. Setup3.00 moles Al x 26.98 g Al = 1 mole Al Answer = 81.0 g Al

23. Converting Moles and Grams Iron (III) oxide is often called rust, it forms when iron metal reacts with moisture. How many moles of Fe2O3 are in 3.00 grams of Fe2O3? 3.00 grams of Fe2O3? moles Fe2O3

24. 1. Molar mass of Fe2O3YOU MUST CALCULATE IT! 2. Conversion factors for Fe2O3 ? g Fe2O3 or 1 mol Fe2O3 1 mol Fe2O3 ? g Fe2O3 3. Setup3.00 grams Fe2O3 x 1 moleFe2O3 ? grams Fe2O3 Answer = 0.0188 mol Fe2O3

25. 1. Molar mass of Fe2O3159.70 grams 2. Conversion factors for Fe2O3 159.70 g Fe2O3 or 1 mol Fe2O3 1 mol Fe2O3 159.70 g Fe2O3 3. Setup3.00 grams Fe2O3 x 1 moleFe2O3 159.70 g Fe2O3 Answer = 0.0 188 mole Fe2O3

26. Learning Check! The artificial sweetener aspartame (Nutra-Sweet) formula C14H18N2O5 is used to sweeten diet foods, coffee and soft drinks. How many moles of aspartame are present in 225 g of aspartame?

27. Setting it up: 225 g C14H18N2O5 = ? mol C14H18N2O5 225g x _?__mol__ = mol ? g Do you know a relationship between moles and grams for C14H18N2O5 ?

28. Setting it up: 225 g C14H18N2O5 = ? mol C14H18N2O5 The relationship is: MOLAR MASS! 1 mol = the sum of the atomic masses from the periodic table in grams! 225g x _1__mol__ = ? mol ? g

29. Setting it up: 225 g C14H18N2O5 = ? mol C14H18N2O5 225g x _1__mol__ = ? mol 294.34 g How do you enter this in your calculator? Enter first number first, multiply numerators, divide by denominators. 225 x 1 / 294.35 =