1. Unit 8 Chemical Quantities Chemistry I Mr. Patel SWHS

2. Topic Outline MUST have a scientific calculator (not graphing)!!! Review of Factor-label Method The Mole and Particle to Mole Conversion (10.1) Molar Mass and Gram to Mole Conversion (10.2) Chemical Formula as a Conversion Factor (N/A) Solution Concentration (16.2) Percent Composition (10.3) Empirical and Molecular Formulas (10.3)

3. Conversion Factors Conversion factor – allows us to convert from one unit to another unit – Example: 1m = 1000mm, 1 dozen = 12 items We use the factor label method to convert Old Unit New UnitGiven = Desired Quantity Remember: Multiply the top Divide the bottom

4. Measuring by Count A count refers to a grouping or a word representing a number – Pair (2), Dozen (12), Ream (500) A count is a conversion factor – can convert between a count unit and the number of items – Ex: 1 dozen egg is the same as 12 actual eggs

5. Ex: Convert 3 dozen apples to number of apples. Use the factor-label method. 1 dozen apples 12 apples3 dozen apples = 36 apples

6. Representative Particle Representative Particle – species present in a particle – Atoms (elements; ex: Fe atom) – Molecules (covalent compounds; ex: diatomics) – Ions (species with a charge; ex: Na 1+ ) – Formula Units (ionic compounds; ex: NaCl)

7. The Mole The fundamental count in chemistry is the mole – SI unit for amount – Very similar to a dozen; represents a number – Abbreviation: mol – Contains an Avogadro’s Number of items – Avogadro’s Number = 6.02 x 10 23

8. The Mole It is not appropriate to consider only one atom of an element or one formula unit of a compound – It is easier to group atoms using a large number – NOTE: 1 mole contains the same number of item…but does not necessarily have the same mass!!!

9. The Mole Just like a dozen, the mole is a conversion factor! We can convert between the unit (mole) and the number of items Remember: – 1 mole X = 6.02 x 10 23 X – You can substitute any item for the X

10. Ex: Convert 1 mole of Fe to number of Fe atoms. Use the factor-label method. 1 mol Fe 6.02 x 10 23 atoms Fe 1 mol Fe = 6.02 x 10 23 atoms Fe Math: (1) x (6.02 x 10 23 ) / (1) = 6.02 x 10 23

11. Ex: Convert 7.8 mol of clipped fingernails to number of clipped fingernails (CF). Use the factor-label method. 1 mol CF 6.02 x 10 23 CF 7.8 mol CF = 4.7 x 10 24 CF Math: (7.8) x (6.02 x 10 23 ) / (1) = 4.7 x 10 24

12. Ex: Convert 2.1 x 10 9 atoms of Li to moles of Li. Use the factor-label method. 6.02 x 10 23 atoms Li 1 mol Li 2.1 x 10 9 atom Li = 3.49 x 10 -15 mol Li Math: (2.1 x 10 9 ) x (1) / (6.02 x 10 23 ) = 3.49 x 10 -15