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Chemistry 20 Mole Conversions What is a Mole? • A term of measurement • A counting number –Similar to saying 1 dozen = 12 things • Avogadro's Number (NA) = 1 mole 6.02 x 1023 items A VERY LARGE NUMBER!!! • 3.00 moles of little green peas would cover 250 planets the size of Earth 1m deep in green peas • 1.00 mole of basketballs would fill a bag the size of the Earth Mole Conversions Molar Mass Mass In Grams Moles g/mol Molar Mass • Molar mass is the mass of one mole in an element or compound • Atomic mass tells us that the units are grams per mole g/mol Examples: Carbon, C = 12.01 g/mol Phosphorus, P = 30.97 g/mol Molar Mass Examples What is the Molar Mass of: Salt, NaCl: Na = 22.99g/mol Cl = 35.45g/mol NaCl = 22.99g/mol + 35.45g/mol = 58.44g/mol Glucose, C6H12O6: C6 = 6(12.01g/mol) H12 = 12(1.01g/mol) O6 = 6(16.00g/mol) C6H12O6 = 6(12.01g/mol) +12(1.01g/mol) 6(16.00g/mol) = 180.18 g/mol Sodium bicarbonate, NaHCO3: Na= 22.99g/mol H=1.01g/mol O = 3(16.00g/mol) C=12.01g/mol NaHCO3= 22.99g/mol + 1.01g/mol + 12.01g/mol + 3(16.00g/mol) = 84.01g/mol Mole Conversion Examples A grade eleven chemistry student has 3.00 g of boron tribromide (BBr3). How many moles of BBr3 is this? Molar mass of BBr3 = 10.81 + 3(79.90) = 250.51g/mol 3.00g BBr3 x 1mole 250.51g = 0.0120 mole BBr3 REMEMBER SIG FIGS! If I have 50.0g of calcium chlorate Ca(ClO3)2 how many moles do I have? Molar Mass Ca(ClO3)2 = (40.08) + 2(35.45) + 6(16.00) = 206.98 g/mol 50.0g Ca(ClO3)2 x 1 mole = 0.242 mole Ca(ClO3)2 206.98g Sig Figs Determine the mass of the following amount: 6.94 mol barium chloride (BaCl2) Molar Mass BaCl2 = 137.33 + 2(35.45) = 208.23 g/mol 6.94 mol BaCl2 x 208.23 g = 1.45 x 103 g BaCl2 1 mole Remember only 3 sig figs Chemistry 20 Mole Conversions Mole Conversions Avogadro’s Number Respective Particles Moles 6.02 x 1023 molecules or atoms or formula units Mole Conversion Examples If a chemist is experimenting with 5 700 000 000 atoms of lead how many moles is she dealing with? Avogadro’s number = 6.02 x 1023 atoms 5 700 000 000 atoms Pb x 1 mole = 9.5 x 10-15 mol 2 sig figs 6.02 x 1023 atoms 2 sig figs How many moles is in 2.97 x 1025 atoms of Vanadium? 2.97 x 1025 atoms of V x 1 mole 6.02 x 1023 atoms = 49.3 moles of V Determine the number of molecules in the following: a) 1.01 moles of bismuth 6.02 x 1023 atoms 1 mole = 6.08 x 1023 atoms of Bi 1.01 mol Bi x b) 2.5 moles of manganese 2.5 mol Mn x 6.02 x 1023 atoms 1 mole = 1.5 x 1024 atoms of Mn If the students in a chemistry 20 class have 7.66 x 1019 molecules of hydrogen peroxide, H2O2, how many moles do they have? 7.66 x 1019 molecules x 1 mole 6.02 x 1023 molecules = 1.27 x 10-4 molecules of H2O2 Chemistry 20 Mole Conversions Mole Conversions Litres of Gas at STP Volume Moles 22.4 L Mole Conversion Examples Determine the volume, in liters, occupied by 0.030 moles of helium gas at STP. 0.030 moles He(g) x 22.4L 1 mole = 0.67 L of He(g) REMEMBER UNITS What is the volume of 0.05 mol of neon gas at STP? 0.05 mol Ne x 22.4L = 1.12L of Ne(g) 1 mole How many moles of argon atoms are present in 11.2 L of argon gas at STP? 11.2L Ar(g) x 1 mole = 0.5 mole Ar(g) 22.4L What is the volume of 1.2 moles of water vapor at STP? 1.2 mol H2O(g) x 22.4L = 26.88L of H2O 1 mole Chemistry 20 Mole Conversions Mole Conversions Representative Particles x 6.02 x 1023 particles 1 mole x 1 mole 6.02 x 1023 particles MOLE x 1mole molar mass X 22.4L 1 mole Volume at STP x 1 mole 22.4L x molar mass 1mole Mass Mixed Mole Conversion 1. Write down the question’s the given and the unknown. 2. Convert the given unit to number of moles. 3. Convert the number of moles found to the unknown unit. 4. Make sure the answer has the correct unit and number of sig figs. Mole Conversion Examples Calculate the mass, in grams (g), of the following: a) 3.00L of O2(g) 3.00L of O2(g) x 1 mole x 32.00 g = 4.29 g O2(g) 22.4L 1mole b) 15 atoms of gold 15 atoms Au(s) x 1 mole x 196.97g = 4.9 x 10-21 g Au 6.02 x 1023 atoms 1 mole Calculate the number of atoms in 2.0L of SO3 gas. 2.0L SO3(g) x 1 mole x 6.02 x 1023 atoms = 5.3 x 1022 atoms SO3 22.4 L 1 mole If the students in a Chemistry 20 class have 3.25 x 105 molecules of CO2(g), how many litres do they have? 3.25 x 105molecules of CO2(g) x 1 mole = 5.40 x 10-29 mole 6.02 x 1023 molecules 5.40 x 10-29 mole CO2 x 22.4L = 1.21 x 10-17 L CO2 1 mole