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THE MOLE ... a unit of counting Review • How many oxygen atoms in the following? CaCO3 Al2(SO4)3 3 atoms of oxygen x 6.022 x 10 23 12 atoms of oxygen x 6.022 x 10 23 • How many ions in the following? 3 total ions x 6.022 x 10 23 CaCl2 NaOH Al2(SO4)3 2 total ions x 6.022 x 10 23 5 total ions x 6.022 x 10 23 N = nNA Finding Number of Atoms or Molecules How many atoms of copper are there in 2.0 moles? Given: n Cu = 2.0 mol NA = 6.02 X 1023 N = nNA = 2.0 mol X 6.02 X 1023 atoms 1 mol = 1.2 X1024 atoms of copper How we measure moles… • Do you know how to measure out 3 moles of sugar or salt or water? – The mole is a counting unit, so we would have to count out 6.02x1023 particles of each substance. (no thank you) • There are 2 ways we can use to measure out a number of moles of a substance. – Measure it in grams (a mass) – Or measure it in liters (a volume) Using a formula • N = Number of particles , ions, atoms, • • • • molecules or formula units NA = Avogadros number n = number of moles n = N / NA N = n x NA • Note on calculator x 10 is • N n NA the same as EXP or EE. DO NOT use them both On calculator use 6.022 EXP 23 Mole Calculations MM = m/n m n = m/MM MM n m = MMn Factor Label! Let the units guide you N = nNA n = N/NA Determining Molar Mass The mass of one mole is called “molar mass” E.g. 1 mol Li = 6.94 g Li This is expressed as 6.94 g/mol Symbol MM What is the molar mass of CO2? Recall: Add the individual molar masses MM(NH4)3PO4 = = = = 3(N + 4H) + P + 4O 3N + 12H + P + 4O 3(14.01) + 12(1.01) + 30.97 + 4(16.00) 149.12 g/mol The same as: Gram Molecular Mass (for molecules) Gram Formula Mass (ionic compounds) Gram Atomic Mass (for elements) molar mass is just a much broader term than these other specific masses MM = m/n n = m/M m = Mn Converting Mass to Moles Example: How many moles of calcium carbonate are there in 1.5 kg? n = m/MM Given: = 1500 g 100.09 g/mol m CaCO3 = 1500 g = 15 mol MM = 40.08 + 12.01 + (3 X 16.00) = 100.09 g/mol n = 1500 g X 1 mol 100.09 g = 15 mol MM = m/n n = m/M m = Mn Converting Moles to Mass Example: What is the mass in grams of 0.346 mol of sodium sulfate? m = MMn Given: n Na2SO4 = 0.346 mol MM = (2 X 22.99) + 32.06 + (4 X 16.00) = 142.04 g/mol = 142.04 g X 0.346 mol 1 mol = 49.1 g Try These: How much would 2.34 moles of carbon weigh? 28.1 grams C How many moles of magnesium is 24.31 g of Mg? 1.000 mol Mg How many sugar (sucrose, C12H22O11) molecules are there in a 1.00 kg bag? Given: m = 1.00 X 103 g MM = (12 X 12.01) + (22 X 1.01) + (11 X 16.00) = 342.34 g/mol n = 1.00 X 103 g X 1 mol 342.34 g = 2.921 mol N = nNA = 2.921 mol X 6.02 X 1023 molecules 1 mol = 1.76 X1024 molecules of sugar How many carbon atoms are there in a 1.00 kg bag of sugar (sucrose, C12H22O11) ? N = 1.76 X 1024 molecules of sugar X 12 carbon atoms 1 molecule sugar = 2.11 X 1025 carbon atoms Mass Concentration (mol/L) (g) Moles (mol) # of molecules/ atoms/ions Volume (L) at STP (0˚C, 101.3 kpa) Learning check 1.How many atoms of Cu are present in 35.4 g of Cu? = 3.35 X 1023 atoms Cu How many atoms of K are present in 78.4 g of K? = 1.21 X 1024 atoms K What is the mass of 1.20 x 1024 molecules of glucose (C6H12O6)? 2. 3. = 359 g Learning Check! How many atoms of O are present in 78.1 g of oxygen? 78.1 g O2 1 mol O2 6.02 X 1023 molecules O2 2 atoms O 32.0 g O2 1 mol O2 1 molecule O2 Measuring volume MOLAR VOLUME, Vm Volume occupied by 1 mole of any gas 22.4 L at STP (standard temperature and pressure) at 0°C and 1 atmosphere/ 103kPa (kilopascals) 24.8 L at SATP Standard Ambient Temperature and Pressure ( 20oC and 1 atmosphere ) Particles to moles or moles to particles Mass to moles or moles to mass Volume to moles and moles to volume V = n x Vm HOMEWORK • Finish Grams-Mole • Worksheet Mole Worksheet – Due Tuesday, April 9th