Counting Atoms and Ions in Chemistry

1. THE MOLE ... a unit of counting

2. Review How many oxygen atoms in the following? CaCO 3 Al 2 (SO 4 ) 3 How many ions in the following? CaCl 2 NaOH Al 2 (SO 4 ) 3 3 atoms of oxygen x 6.022 x 10 23 12 atoms of oxygen x 6.022 x 10 23 3 total ions x 6.022 x 10 23 2 total ions x 6.022 x 10 23 5 total ions x 6.022 x 10 23

3. Finding Number of Atoms or Molecules How many atoms of copper are there in 2.0 moles? N = nN A Given: n Cu = 2.0 mol N A = 6.02 X 10 23 N = nN A = 2.0 mol X 6.02 X 10 23 atoms 1 mol = 1.2 X10 24 atoms of copper

4. 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 6.02x10 23 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 ) 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 6.02x10 23 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 ) How we measure moles How we measure moles

5. Using a formula N = Number of particles , ions, atoms, molecules or formula units N A = Avogadros number n = number of moles n = N / N A N = n x N A Note on calculator x 10 is the same as EXP or EE. DO NOT use them both On calculator use 6.022 EXP 23 N N A n

6. Mole Calculations MM m n MM = m/n n = m/MM m = MMn Factor Label! Let the units guide you N = nN A n = N/N A

7. 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 CO 2 ? Recall: Add the individual molar masses MM (NH 4 ) 3 PO 4 = 3(N + 4H) + P + 4O = 3N + 12H + P + 4O = 3(14.01) + 12(1.01) + 30.97 + 4(16.00) = 149.12 g/mol

8. The same as: G ram M olecular M ass (for molecules) G ram F ormula M ass (ionic compounds) Gram A tomic M ass (for elements) molar mass is just a much broader term than these other specific masses

9. Converting Mass to Moles Example: How many moles of calcium carbonate are there in 1.5 kg? MM = m/n n = m/M m = Mn Given: m CaCO 3 = 1500 g MM = 40.08 + 12.01 + (3 X 16.00) = 100.09 g/mol n = m/MM = 1500 g 100.09 g/mol = 15 mol n = 1500 g X 1 mol 100.09 g = 15 mol

10. Converting Moles to Mass Example: What is the mass in grams of 0.346 mol of sodium sulfate? MM = m/n n = m/M m = Mn Given: n Na 2 SO 4 = 0.346 mol MM = (2 X 22.99) + 32.06 + (4 X 16.00) = 142.04 g/mol m = MMn = 142.04 g X 0.346 mol 1 mol = 49.1 g

11. Try These: How much would 2.34 moles of carbon weigh? How many moles of magnesium is 24.31 g of Mg? 28.1 grams C 1.000 mol Mg

12. How many sugar (sucrose, C 12 H 22 O 11 ) molecules are there in a 1.00 kg bag? Given: m = 1.00 X 10 3 g MM = (12 X 12.01) + (22 X 1.01) + (11 X 16.00) = 342.34 g/mol n = 1.00 X 10 3 g X 1 mol 342.34 g = 2.921 mol N = nN A = 2.921 mol X 6.02 X 10 23 molecules 1 mol = 1.76 X10 24 molecules of sugar

13. How many carbon atoms are there in a 1.00 kg bag of sugar (sucrose, C 12 H 22 O 11 ) ? N = 1.76 X 10 24 molecules of sugar X 12 carbon atoms 1 molecule sugar = 2.11 X 10 25 carbon atoms

14. Moles (mol) Mass (g) # of molecules/ atoms/ions Volume (L) at STP (0C, 101.3 kpa) Concentration (mol/L) 6.02 X 10 23 g/mol 22.4 Vol

16. Learning check 1. How many atoms of Cu are present in 35.4 g of Cu? 2. How many atoms of K are present in 78.4 g of K? 3. What is the mass of 1.20 x 10 24 molecules of glucose (C 6 H 12 O 6 )? = 3.35 X 10 23 atoms Cu = 1.21 X 10 24 atoms K = 359 g

17. Learning Check! Learning Check! How many atoms of O are present in 78.1 g of oxygen? 78.1 g O 2 1 mol O 2 6.02 X 10 23 molecules O 2 2 atoms O 32.0 g O 2 1 mol O 2 1 molecule O 2

18. Measuring volume MOLAR VOLUME, Vm Volume occupied by 1 mole of any gas 22.4 L at STP ( standard temperature and pressure ) at 0C and 1 atmosphere / 103kPa (kilopascals) 24.8 L at SATP Standard Ambient Temperature and Pressure ( 20 o C and 1 atmosphere )

19. 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

20. HOMEWORK Finish Grams-Mole Worksheet Mole Worksheet Due Tuesday, April 9th