1. Moles, Molecules and Atoms

2. How you measure how much? You can measure mass, or volume, or you can count pieces. We measure mass in grams. We measure volume in liters. We count pieces in MOLES.

3. The Mole Defined as the number of carbon atoms in exactly 12 grams of carbon-12. 1 mol is 6.02 x 10 23 1 mol is 6.02 x 10 23 representative particles Treat it like a very large dozen 6.02 x 10 23 is called Avogadro’s number.

4. Representative Particles The smallest pieces of a substance. For a molecular compound, it is a molecule. For an ionic compound, it is a formula unit. (or individual ions) For an element, it is an atom.

5. Determining the Molar Mass The mass of one mole of a substance in grams. For an Element: For an Element: Gram Atomic Mass (GAM) Use average atomic mass or atomic weight from periodic table. Examples: Calcium Iron

6. For a Compound In 1 mol of H 2 O molecules, there are two moles of H atoms and 1 mole of O atoms To find the mass of one mole of a compound determine the moles of the elements contained in compound Find out their molar mass Add them up

7. For a compound cont’ For an ionic compound: Gram Formula Mass GFM For a molecular compound: Gram Molecular Mass GMM Example: Example: Calculate the gram formula mass of gold (III) oxide. Au 2 O 3

8. More Examples: Calculate the molar mass of the following: 1. Na 2 SO4 2. Al( N O 3 ) 3 3. CO 2

9. Review Problems 1. Ca(NO 3 ) 2 2. C 6 H 12 O 6 3. (NH 4 ) 3 PO 4

10. Dimensional Analysis using moles, grams and Avogadro’s Number

11. Dimensional Analysis Review: 1. A student lives 3,500 ft from the high school. Determine the distance in miles. 2. A child drinks 2.0 liters of Mountain Dew for breakfast before school. How many gallons of soda did he consume?

12. Finding the Conversion Factor 1 mol = molar mass (g) = 6.02 X 10 23 particles Ex. What is the molar mass of ethanol (C 2 H 5 OH)? Therefore 1 mol of ethanol has a mass of 46.069-g and contains 6.02 X 10 23 molecules of ethanol.

13. Types of Problems: 1. If a scientist needs 2.75 mol of ethanol to complete an experiment, how many grams of the substance does she need? 2. If the density of ethanol is 0.791 g/mL, how many milliliters would she measure out?

14. Types of Problems: 3. Calculate the number of molecules of water contained in a 12.3-g sample of the liquid. 4. A sample of carbon contains 9.67 X 10 24 atoms. What is the mass of the sample?

15. Types of Problems: 5. A sample of carbon tetrachloride contains 4.51 X 10 22 molecules. What is the mass of the sample of carbon tetrachloride?

16. Types of Problems: 6. Isopentyl acetate (C 7 H 14 O 2 ) is the compound responsible for the scent of bananas. Bees release about 1.00 X 10 -6 grams of this compound when they sting. The resulting scent attracts other bees to join the attack. How many molecules of isopentyl acetate are released in a bee sting?

17. Molar Volume of a Gas At STP, 1 mol or 6.02 X 10 23 molecules of any gas occupies a volume of 22.4-L. STP = Standard Temperature and Pressure The converting factor: 1 mol = 22.4 L of a gas

18. Examples: 1. Sulfur dioxide is a gas produced by burning coal. Determine the volume, in liters, of 0.60 mol of SO 2 at STP. 2. At STP, calculate the number of moles of carbon dioxide gas in a 14.2-L sample of the gas.