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Mole Problems

Mole Problems. Calculating molar mass. Round all masses to the 10ths place. Calculate the molecular weight of F e 2 O 3. Step One: two atoms of iron and three of oxygen Step Two: Fe = 55.8 amu and O = 16.0 amu Step Three: (2 x 55.8) + (3 x 16.0)

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Mole Problems

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  1. Mole Problems

  2. Calculating molar mass Round all masses to the 10ths place

  3. Calculate the molecular weight of Fe2O3 • Step One: two atoms of iron and three of oxygen • Step Two: Fe = 55.8 amu and O = 16.0 amu • Step Three: (2 x 55.8) + (3 x 16.0) • Step Four: 111.6 + 48.0 = 159.6 amu (grams) for one mole

  4. Calculate the molecular weight of KClO4 • Step One: one atom of potassium, one of chlorine, and four of oxygen. • Step Two: K = 39.1 amu, Cl = 35.5 amu, O = 16.0 amu • Step Three: (1 x 39.1) + (1 x 35.5) + (4 x 16.0) • Step Four: 39.1 + 35.5 + 64.0 = 138.6 amu (grams) for one mole

  5. Calculate the molecular weight of (NH4)2S • Step One: two atoms of nitrogen, eight of hydrogen and one of sulfur • Step Two: N = 14.0 amu, H = 1.0 amu, S = 32.1 amu • Step Three: (2 x 14.0) + (8 x 1.0) + (1 x 32.1) • Step Four: 28 + 8.0 + 32.1 = 68.1 amu (grams) for one mole

  6. Calculate the molar mass of Al(NO3)3 • Calculate the molar mass of Al(NO3)3 • Al(1 x 27.0) + N(3 x 14.0) + O(9 x 16.0) = • 213.0 amu (grams) is the mass of one mole of aluminum nitrate.

  7. You Try These… • 1. AlCl3 • 2. Ba(SCN)2 • 3. LiH • 4. Ba(BrO3)2 • 5. AlBr3 • 6. HCl

  8. Answers • 1. 133.5 g/mol • 2. 253.5 g/mol • 3. 7.9 g/mol • 4. 393.1 g/mol • 5. 266.7 g/mol • 6. 36.5 g/mol

  9. GRAMS to MOLES Round all final answers to 3 sig figs

  10. Convert 25.0 grams of KMnO4to moles. • KMnO4 =158.0 g / mole of KMnO4 • Now let’s solve it • 25.0 g x 1 mole = 0.158191804 moles 158.0 g • 0.158 moles

  11. Calculate how many moles are in 17.0 grams of H2O2. • H2O2 = 34.0 g / mole • Now, let’s solve it • 17.0 g x 1 mol H2O2= 0.5 moles 34.0 g • 0.500 moles

  12. You try these… • Calculate the moles present in: • 1) 2.00 grams of H2O • 2) 75.57 grams of KBr • 3) 100. grams of KClO4 • 4) 8.76 grams of NaOH • 5) 0.750 grams of Na2CO3 • Remember to round answers to 3 sig figs

  13. Answers • 1) 0.111 moles • 2) 0.635 moles • 3) 0.722 moles • 4) 0.219 moles • 5) 0.00708 moles

  14. MOLES TO GRAMS Round all answers to 3 sig figs

  15. Calculate how many grams are in 0.700 moles of H2O2 • H2O2 molar mass = 34.0 grams/mole • 0.700 moles x 34.0 grams = 23.8 g 1 mole • 23.8 grams

  16. Convert 2.50 moles of KClO3 to grams. • KClO3 molecular mass = 122.6 g/mole • 2.50 moles x 122.6 g = 306.5 grams 1 mole • 307 grams

  17. You try these… • Calculate the grams present in: • 1) 0.200 moles of H2S • 2) 0.100 moles of KI • 3) 1.500 moles of KClO • 4) 0.750 moles of NaOH • 5) 3.40 x 10-5 moles of Na2CO3 • Remember to round answer to 3 sig figs

  18. Answers • 1) 6.82 grams • 2) 16.6 grams • 3) 136 grams • 4) 30.0 grams • 5) 0.00360 grams

  19. Avogadro's Number 6.02 x 1023 particles = 1 mole Particles can mean atoms or molecules

  20. One mole of ANY specified entity contains 6.02 x 1023 of that entity

  21. For Example • One mole of donuts contains 6.02 x 1023 donuts • One mole of H2O contains 6.02 x 1023 molecules • One mole of nails contains 6.02 x 1023 nails • One mole of Fe contains 6.02 x 1023 atoms

  22. Continued • One mole of dogs contains 6.02 x 1023 dogs • One mole of electrons contains 6.02 x 1023 electrons • One mole of Chemistry students contains 6.02 x 1023 poor, suffering (I mean happy, joyful) high school students

  23. 0.450 mole of Fe contains how many atoms? • 0.450 mole Fe x 6.02 x 1023 atoms 1 mole • = 2.709x1023 atoms • Final, rounded answer: 2.71x1023 atoms

  24. 0.200 mole of H2O contains how many molecules? • 0.200 mole x 6.02 x 1023 atoms 1 mole • = 1.204x1023 atoms • Final, rounded answer: 1.20x1023 atoms

  25. You try these… • 1) Calculate the number of molecules in 1.058 mole of H2O • 2) Calculate the number of atoms in 0.750 mole of Fe • Remember to round to 3 sig figs

  26. Answers • 1) 6.37x1023 molecules • 2) 4.52x1023 atoms

  27. Two Step Problems Grams to particles OR particles to grams Grams to atoms OR atoms to grams If MOLE is not stated, it’s a two step problem ROUND ALL ANSWERS TO 3 SIG FIGS

  28. 0.450 gram of Fe contains how many atoms? • 0.450 g x 1 mole Fe x 6.02x1023 atoms = 55.8 g 1 mole • 4.8548387x1021 atoms • Final answer = 4.85x1021 atoms

  29. 0.200 gram of H2O contains how many molecules? • H2O molecular mass = 18.0 g • 0.200 g x 1 mole H2O x 6.02x1023 molecules 18.0 g 1 mole • 6.6888888889x1021 molecules • Final answer = 6.69x1021molecules

  30. You try these… • 1) Calculate the number of molecules in 1.058 gram of H2O • 2) Calculate the number of atoms in 0.750 gram of Fe • Remember to round answer to 3 sig figs

  31. Answers • 1) 3.54x1022 molecules • 2) 8.10x1021 atoms

  32. THE END

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