Formula ppt
- 1. The Mole Formula Calculations I II III
- 2. A. Percentage Composition s the percentage by mass of each element in a compound mass of element % compositio n = × 100 total mass
- 3. A. Percentage Composition s Find the % composition of Cu2S. 127.10 g Cu %Cu = × 100 = 159.17 g Cu2S 79.852% Cu 32.07 g S %S = × 100 = 159.17 g Cu2S 20.15% S
- 4. A. Percentage Composition s Find the percentage composition of a sample that is 28 g Fe and 8.0 g O. 28 g %Fe = × 100 = 78% Fe 36 g 8.0 g %O = × 100 = 22% O 36 g
- 5. A. Percentage Composition s How many grams of copper are in a 38.0-gram sample of Cu2S? Cu2S is 79.852% Cu (38.0 g Cu2S)(0.79852) = 30.3 g Cu
- 6. A. Percentage Composition s Findthe mass percentage of water in calcium chloride dihydrate, CaCl2•2H2O? %H2O = 36.04 g × 100 = 24.51% 147.02 g H2O
- 7. B. Empirical Formula s Smallestwhole number ratio of atoms in a compound C2H6 reduce subscripts CH3
- 8. B. Empirical Formula 1. Find mass (or %) of each element. 2. Find moles of each element. 3. Divide moles by the smallest # to find subscripts. 4. When necessary, multiply subscripts by 2, 3, or 4 to get whole #’s.
- 9. B. Empirical Formula s Find the empirical formula for a sample of 25.9% N and 74.1% O. 25.9 g 1 mol = 1.85 mol N =1N 14.01 g 1.85 mol 74.1 g 1 mol = 4.63 mol O = 2.5 O 16.00 g 1.85 mol
- 10. B. Empirical Formula N1O2.5 Need to make the subscripts whole numbers ⇒ multiply by 2 N2O5
- 11. C. Molecular Formula s “True Formula” - the actual number of atoms in a compound CH3 empirical formula ? C2H6 molecular formula
- 12. C. Molecular Formula 1. Find the empirical formula. 2. Find the empirical formula mass. 3. Divide the molecular mass by the empirical mass. 4. Multiply each subscript by the answer from step 3. MF mass EF mass =n ( EF ) n
- 13. C. Molecular Formula s The empirical formula for ethylene is CH2. Find the molecular formula if the molecular mass is 28.1 g/mol? empirical mass = 14.03 g/mol 28.1 g/mol = 2.00 14.03 g/mol (CH2)2 ⇒ C2H4