1 Warm Up Isotopes Mass of Isotope Abundance 24 Mg =24.0 amu 78.70% 25 Mg = 25.0 amu 10.13% 26 Mg = 26.0 amu 11.17% Calculate the mass average of magnesium. (24)(.787) + (25)(.1013) + 26(.1117) = = 24.3 amu

2 What is a Mole in Chemistry? (3.1,3.2)

3 Today’s Learning Objectives 1.Understand what a mole is in chemistry 2.Know the relationship of Avogadro’s number to the mole 3.Be able to calculate molar mass (molecular weight) of an element and a compound 4.Be able to convert back and forth between moles and molecules and grams * An appreciation for how big Avogadro’s number really is*

4 What if you had … 2 pairs of shoes = 4 shoes 3 dozen eggs = 36 eggs Do you know how many eggs are in a flat? In a crate? Do you know how many carbon atoms are in a _______? mole

5 Avogadro’s Number 6.02 X Do you know how many protons are in a mole? Do you know how molecules of H 2 O are in a mole? Do you know how many carbon atoms are in a mole? Do you know how many footballs are in a mole? Do you know how many footballs are in a 2 moles?

6 It’s a big number!!! -It’s 602 billion trillion 602,000,000,000,000,000,000, X (in scientific notation) His most important contribution to chemistry is known as Avogadro’s Law, which states that all gases that are at the same volume, temperature, and pressure contain the same number of molecules. This law allows chemists to calculate the molecular weight of gases, and if the molecular formula is known, the weight of each atom in the gas. Though it was not well received at the time of publication, it was verified by various other scientists after his death. Any chemist will agree that Avogadro’s Law was a massive step forward in the evolution of chemistry. Amedeo Avogadro

7 How was this number discovered? It had been estimated by several scientists over the years with crude experiments, but in 1911 Robert Millikan did his famous oil drop experiment which determined the charge on a single electron. For years scientists had known the charge on a mole of electrons, so a simple calculation led to Avogadro’s number. Scientific American article about discovery of Avogadros number

8 Just How Big is a Mole? Enough soft drink cans to cover the surface of the earth to a depth of over 200 miles. If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole.

9 Defined as: mass of 1 mole of element or molecule (in grams) Equal to the atomic mass from periodic table. Easy!!! 1 mole of C atoms= 12.0 g/mol 1 mole of Mg atoms =24.3 g/mol 1 mole of Cu atoms =63.5 g/mol Molar Mass (Molecular Weight)

10 Molar Mass of Compounds Mass in grams of 1 mole of a compound equals the sum of the molar mass of each element in that compound CaCl 2 = 1 Ca + 2 Cl = 1 x 40.1 g/mol + 2 x 35.5 g/mol = 40.1 g/mol g/mol = g/mol What is the molar mass of CaCl 2 ? Or written in another way …. How much does 1 mole of CaCl 2 weigh?

11 Prozac (flouxetine), C 17 H 18 F 3 NO, is a widely used antidepressant that inhibits the uptake of serotonin by the brain. Find its molar mass. Can you do this!!!! g/mol

12 Moles to Molecules…. If you have moles of barium sulfate, how many molecules of BaSO 4 do you have? moles BaSO 4 1 mole BaSO 4 = 3.80 x molecules BaSO x molecules BaSO 4 Moles x Avogadro’s # = Molecules

13 Molecules to Mole …. If you have 7.36 x molecules of barium sulfate, how many moles of BaSO 4 do you have? 7.36 x molecules BaSO 4 1 mole BaSO 4 = mole BaSO x molecules BaSO 4 Molecules / Avogadro’s # = Moles

14 Grams to Moles …. If you have g of CuHAsO 3. How many moles do you have? g CuHAsO g CuHAsO 3 Cu = 1(63.5) = 63.5 H = 1(1.0) = 1.0 As = 1(74.9) = 74.9 O = 3(16.0) = 48.0 = g/mol 1 mole CuHAsO 3 = mole CuHAsO 3 = mole CuHAsO 3 = x mole CuHAsO 3 Grams / Molar Mass = Moles

15 Moles to Grams …. If you have 1.54 moles of CuHAsO 3. How many grams do you have? 1.54 mol CuHAsO g CuHAsO 3 Cu = 1(63.5) = 63.5 H = 1(1.0) = 1.0 As = 1(74.9) = 74.9 O = 3(16.0) = 48.0 = g/mol 1 mole CuHAsO 3 = g CuHAsO 3 = 289 g CuHAsO 3 (only 3 sig figs) Moles x Molar Mass = Grams

16 All Roads Go Through Mole City Gramville Mole City Multiply by molar mass Gas Station Divide by molar mass Multiply by 6.02 x Divide by 22.4 L Divide by 6.02 x Multiply by 22.4 L Molecule Town

17 Homework Read Problems 7, 17, 20, 26, 29, 31, 34, 39, 54

18 Moles to Liters Liters to Moles Avogadro in 1811 Equal volumes of gases at the same temperature and pressure contain equal number of particles!

19 Molar Volume at STP If you have a 1 mole of gas (6.02 x particles of gas) at Standard Temperature = 0 o C Standard Pressure = 1.00 atm Then you will have 22.4 liters of gas molar volume

20 Molar Volume: What It Means

21 Liters to Moles…. You have L of N 2 gas. How many moles do you have? Liters N Liters N 2 1 mole N 2 = mol N 2 = mol N 2

22 Moles to Liters…. You have.43 moles of F 2 gas. How many liters do you have? 0.43 mol F L of F 2 1 mole F 2 = 9.6 L of F 2