# Counting Atoms and Ions in Chemistry

Learn how to count the number of atoms and ions in chemical compounds using the mole unit and Avogadro's number. Examples include CaCO3, Al2(SO4)3, CaCl2, NaOH, and Cu.

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## About Counting Atoms and Ions in Chemistry

PowerPoint presentation about 'Counting Atoms and Ions in Chemistry'. This presentation describes the topic on Learn how to count the number of atoms and ions in chemical compounds using the mole unit and Avogadro's number. Examples include CaCO3, Al2(SO4)3, CaCl2, NaOH, and Cu.. The key topics included in this slideshow are mole unit, Avogadro's number, atoms, ions, CaCO3, Al2(SO4)3, CaCl2, NaOH, Cu,. Download this presentation absolutely free.

## Presentation Transcript

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