2 Review - The Mole A counting unit Similar to a dozen, except instead of 12, it’s 602,000,000,000,000,000,000,0006.02 X 1023 (in scientific notation)This number is named in honor of Amedeo Avogadro (1776 – 1856)
3 Review - Molar Mass The Mass of 1 mole of substance (in grams) Equal to the numerical value of the average atomic mass (get from periodic table), or add the atoms together for a molecule1 mole of C atoms = g1 mole of Mg atoms = g1 mole of O2 molecules = g1 mole of BCl3 molecules = g
4 Molar Mass of Compounds The molar mass (MM) of a compound is determined the same way, except now you add up all the atomic masses for the compoundEx. Molar mass of CaCl2Avg. Atomic mass of Calcium = 40.08gAvg. Atomic mass of Chlorine = 35.45gMolar Mass of calcium chloride = g/mol Ca + (2 x 35.45) g/mol Cl g/mol CaCl220Ca 17 Cl 35.45
5 Flowchart Atoms or Molecules Moles Mass (grams) Divide by 6.02 X 1023 Multiply by 6.02 X 1023MolesMultiply by atomic/molar mass from periodic tableDivide by atomic/molar mass from periodic tableMass (grams)
6 Practice Calculate the Molar Mass of calcium phosphate Ca3(PO4)2 Formula =Masses elements:Ca: 3 Ca’s X =P: 2 P’s X =O: 8 O’s X =Molar Mass =Ca3(PO4)2g61.94 gg120.24g g gg/mol
7 Everything must go through Moles!!! Calculationsmolar mass Avogadro’s number Grams Moles particlesEverything must go through Moles!!!
8 Atoms/Molecules and Grams How many atoms of Cu are present in 35.4 g of Cu?35.4 g Cu mol Cu X 1023 atoms Cu g Cu mol Cu= 3.36 X 1023 atoms Cu
9 Learning Check!What is the mass (in grams) of 1.20 X 1024 molecules of glucose (C6H12O6)?
10 Chocolate Chip Cookies!! 1 cup butter1/2 cup white sugar1 cup packed brown sugar1 teaspoon vanilla extract2 eggs2 1/2 cups all-purpose flour1 teaspoon baking soda1 teaspoon salt2 cups semisweet chocolate chipsMakes 3 dozenHow many eggs are needed to make 3 dozen cookies?How much butter is needed for the amount of chocolate chips used?How many eggs would we need to make 9 dozen cookies?How much brown sugar would I need if I had 1 ½ cups white sugar?
11 Cookies and Chemistry…Huh!?!? Just like chocolate chip cookies have recipes, chemists have recipes as wellInstead of calling them recipes, we call them reaction equationsFurthermore, instead of using cups and teaspoons, we use molesLastly, instead of eggs, butter, sugar, etc. we use chemical compounds as ingredients
12 Chemistry Recipes STOICHIOMETRY Looking at a reaction tells us how much of something you need to react with something else to get a product (like the cookie recipe)The study of the quantative relationships among the amounts of reactants used and the amounts of products formed by a chemical reaction is calledSTOICHIOMETRY
13 Chemistry RecipesBe sure you have a balanced reaction before you start!Example: 2 Na + Cl2 2 NaClThis reaction tells us that by mixing 2 moles of sodium with 1 mole of chlorine we will get 2 moles of sodium chlorideWhat if we wanted 4 moles of NaCl? 10 moles? 50 moles?
14 PracticeWrite the balanced reaction for hydrogen gas reacting with oxygen gas.2 H2 + O2 2 H2OHow many moles of reactants are needed?What if we wanted 4 moles of water?What if we had 3 moles of oxygen, how much hydrogen would we need to react and how much water would we get?What if we had 50 moles of hydrogen, how much oxygen would we need and how much water produced?2 mol H2 1 mol O24 mol H2 2 mol O26 mol H2, 6 mol H2O25 mol O2, 50 mol H2O
15 Mole RatiosThese mole ratios can be used to calculate the moles of one chemical from the given amount of a different chemicalExample: How many moles of chlorine are needed to react with 5 moles of sodium (without any sodium left over)?2 Na + Cl2 2 NaCl5 moles Na 1 mol Cl22 mol Na= 2.5 moles Cl2
16 Mole-Mole Conversions How many moles of sodium chloride will be produced if you react 2.6 moles of chlorine gas with an excess (more than you need) of sodium metal?2 Na + Cl2 2 NaCl
17 Mole-Mass Conversions Most of the time in chemistry, the amounts are given in grams instead of molesWe still go through moles and use the mole ratio, but now we also use molar mass to get to gramsExample: How many grams of chlorine are required to react completely with 5.00 moles of sodium to produce sodium chloride?2 Na + Cl2 2 NaCl5.00 moles Na 1 mol Cl g Cl22 mol Na 1 mol Cl2= 177g Cl2
18 PracticeCalculate the mass in grams of Iodine required to react completely with 0.50 moles of aluminum.2 Al + 3 I2 2 AlI3
19 Mass-MoleWe can also start with mass and convert to moles of product or another reactantWe use molar mass and the mole ratio to get to moles of the compound of interestCalculate the number of moles of ethane (C2H6) needed to produce 10.0 g of water2 C2H6 + 7 O2 4 CO2 + 6 H2010.0 g H2O 1 mol H2O 2 mol C2H618.0 g H2O 6 mol H20= mol C2H6
20 PracticeCalculate how many moles of oxygen are required to make 10.0 g of aluminum oxide4 Al + 3 O2 2 Al2O3
21 Mass-Mass Conversions Most often we are given a starting mass and want to find out the mass of a productThis is called the theoretical yield… or how much of another reactant we need to completely react (with no leftover ingredients!)Now we must go from grams to moles, to the mole ratio, and back to grams of the compound we are interested in
22 Mass-Mass ConversionEx. Calculate how many grams of ammonia are produced when you react 2.00g of nitrogen with excess hydrogen.N2 + 3 H2 2 NH3
23 PracticeHow many grams of calcium nitride are produced when 2.00 g of calcium reacts with an excess of nitrogen?3 Ca + N2 Ca3N2
Your consent to our cookies if you continue to use this website.