Chem the Mole with Answers

Chemistry 11 INTRODUCTION TO UNIT TWO THE MOLE What is a dozen? Consider: the mass of 12 donuts does not equal the mass of 12 timbits OR, consider: 150 g donuts vs. 150 g timbits. You will need a lot more timbits to reach this mass than donuts. Definition of the mole: the number of particles in exactly 12 g of the isotope Carbon -12. OR The number of carbon-12 atoms in 12 grams of unbound carbon in the ground state. That number is 6.02 x 1023 (“Avogadro's number”) Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto 9 August 1776, Turin, – 9 July 1856 For example: B5 (atomic number 5) The mass of one Boron atom is 10.8 amu. “atomic mass units” This mass is compared to the Carbon-12 isotope. AMU is our standard to compare to! It is 1/12 of the C-12 atom. This is equivalent to 1.66 x 10-27 kg. 6. 02 x 1023 atoms of Boron are contained in 10.8 g of Boron. We say that the atomic mass is 10.8 g / mole. ( g / mole is a much more use-able unit to use than “amu”, especially when we have to do unit cancelling calculations) For example. The ionic compound, Calcium Sulphide. Chemical Formula CaS. 23 1 mole sulphur = 32.1 g That’s 6.02 x 10 sulphur atoms having a mass of 32.1g But we also say 1 sulphur atom = 32.1 amu 23 1 mole Ca = 40.1 g That’s 6.02 x 10 calcium atoms having a mass of 40.1g 1 Ca atom = 40.1 amu BUT, we can't work with amu, because this is only 1 molecule or compound or atom or element! Therefore it is more practical to talk about 1 mole of CaS molecules (or 6.02 x 1023 CaS molecules) = 72.1 g. So we would say that the molar mass of CaS is 72.1 g/mole. Also stated as molecular mass. The Mole and History of The Term "Mole" Avogadro's number, the number of particles in a mole, can be experimentally determined by first "counting" the number of atoms in a smaller space and then scaling up to find the number of particles that would have a mass equal to the atomic or molecular mass in grams. The History of the Term"Mole" The Avogadro constant is named after the early nineteenth century Italian scientist Amedeo Avogadro, who is credited (1811) with being the first to realize that the volume of a gas (strictly, of an ideal gas) is proportional to the number of atoms or molecules. The French chemist Jean Baptiste Perrin in 1909 proposed naming the constant in honor of Avogadro. Real World Moles Given that the volume of a grain of sand is approximately 10-12 m3, and given that the area of the United States is about 1013m2, it therefore follows that a mole of sand grains would cover the United States in approximately one centimeter of sand. A human body contains very roughly one hundred trillion cells; there are roughly six billion people on Earth; so the total number of human cells on the planet is approximately 100×1012*6×109=6×1023, which is very close to one mole. Since the Earth has a radius of about 6400 km, its volume is approximately 1021 m3. Since about 500 large grapefruit will fit in one cubic meter, it therefore follows that a mole of grapefruit would have approximately the same volume as the Earth. If you had a mole of pennies, you could give out enough money to everyone in the world so that they could spend a million dollars every hour, day and night, for the rest of their lives. ONE DOZEN can be: 12 dinner rolls 12 eggs 12 roses 12 blood cells (microscopic things too!) 12 of anything!!!!! Similarily, ONE MOLE Can be: 6. 02 x 1023 atoms 6. 02 x 1023 molecules 6. 02 x 1023 protons 6. 02 x 1023 ions 6. 02 x 1023 of anything!!!! Check each of the following, to be sure that you understand how these molar masses were arrived at: SUBSTANCE MOLAR MASS Cu 63.5 g / mole Sn 118.7 g / mole H2 O 18 g / mole Copper sulphate 159 g / mole 1 mole Cu, 1 mole S, 4 moles O, but only 1 mole CuSO4 !!! potassium chromate 194 g / mole ammonium carbonite 96 g/ mole Chlorine gas Cl2 !!! 71 g / mole Bromine liquid Br2 !!! 1598 g / mole Phosphorus crystals P4 !!! 124 g / mole Copper (I) phosphide 221 g/ mole (Not P4 this time!) COUNTING ATOMS Complete the following table. The first one is done for you. Molecular formula Name # of # of atoms Molecules 3 H2O water 3 6H Ag2CO3 Silver carbonate 1 2Ag 1C 3O Copper (II) nitrate 1 Ammonium sulphide 1 4 CuSO4 3 CaCl2 • 2 H2O Calcium Chloride 3 Dihydrate chloride gas 1 Zinc acetate 1 Magnesium Phosphate 1 Aluminum Oxide Dihydrate 1 6 SnCl2 • 5 H2O 7 LiH2PO4 3O CONVERSION CALCULATIONS Complete the following. You MUST show all of your work in the conversions!!! Show your work on a separate piece of paper. 1) 540 Megabytes of ram = _______________Gigabytes of ram 2) 18fg = ___________Mg 3) 36 pencils = __________ dozen 4) 5 pencils = ___________ dozen 5) 6.02 X 1023 pencils = __________ moles 6) 12.0408 X 1023 pencils = __________ moles 7) 41.0 g N = _______________ moles 8) 41.0 g N = _______________ atoms 9) The mass of 1 atom of nitrogen 10) 2.408 X 1024 ammonia molecules = __________ moles 11) The # of nitrogen atoms in #10: 12) The # of hydrogen atoms in #10: 13) The # of TOTAL atoms in #10: 14) 0.86 moles of ammonia = ______________molecules Starting to draw the mole map: PARTICLES MASS 6.02 x 1023 particles / mole (Avogadro's number) g / mole (molar mass) MOLE Sample calculations WHAT IS THE MASS in grams of one mole of lead? mass = 207 g mole WHAT IS THE MASS in grams of one atom of lead? mass = 207 g x mole 1 mole 6.02 x 1023 atoms X 1 atom = WHAT IS THE MASS in grams of 5.8 x 1025 atoms of lead? mass = 207 g x mole 1 mole 6.02 x 1023 atoms X 5.8 x 10 25 atoms = 1  Mole  Practice  Worksheet  #1     1.  What  is  the  atomic  mass  of…   a)  rubidium         b)  astatine     c)  manganese       2.  What  is  the  molar  mass  of…   a)  gallium  manganate   b)  triiodine  heptafluoride     c)  zinc  carbonate       3.  How  many  moles  are  there  in…   a)  86  g  of  chlorine  gas             b)  258  g  of  tellurium  dioxide  gas       c)  48.00  g  of  carbon  tetrafluoride  gas       4.  What  is  the  mass  in  grams  of…   a)  8  moles  of  ammonia     b)  5.0  moles  of  nitric  acid             c)  0.049  moles  of  hydrogen  chloride       5.  How  many  molecules/atoms  are  there  in  …   a)  4.5  moles  of  neon  gas           b)  1.50  moles  of  nitrogen  dioxide  gas     c)  35.0  g  of  sulphur  difluoride  gas       6.  What  would  be  the  mass  in  grams  of…   a)  6.02  x  1025  atoms  of  osmium   b)  1.53  x  1022  molecules  of  silicon  tetrabromide     Answers   c)  1  molecule  of  water     1.  atomic  mass  means  the  mass  of  a  single  atom   a)  85.5  a.m.u.     b)  210  a.m.u.     c)  54.9  a.m.u.       2.  molar  mass  means  mass  of  1  mole  of  the  substance  in  grams   a)  378  g/mole  Ga(MnO3)3     b)  514  g/mole  I3F7       3.    a)    ?  moles  =  (1  mole  /  71.0  g)  (86  g)  =  1.2  moles  Cl2  (2  sig.  figs.)           b)      1.62  moles  TeO2           c)  0.545  moles  CF4     4.    a)      ?  g  =  (17.0  g  /  mole)  (8  moles)  =  100  g  NH3  (1  sig.  fig.)               b)  320  g  HNO3       c)  1.8  g  HCl     c)  125  g/mole  ZnCO3   5.    a)      ?  molecules  =  (6.02  x  1023  atoms  /  mole)  (4.5  moles)  =  2.7  x  1024  atoms  Ne   b)  9.03  x  1023  molecules  NO2     c)  3.01  x  1023  molecules  SF2       6.    a)      ?g  =  (190.2  g  /  mole)(1  mole  /  6.02  x  1023  atoms)(6.02  x  1025  atoms)  =  1.90  x  104  g     b)  8.84  g  SiBr4         c)  2.99  x  10-­‐23  g  H2O   Mole Calculations Worksheet #2 1. How many moles of Na are in 42 g of Na? 2. How many moles of O are in 8.25 g of O? 3. How much does 2.18 mol of Cu weigh? 4. What is the mass of 0.28 mol of iron? 5. How many atoms are in 7.2 mol of chlorine? 6. How many atoms are in 36 g of bromine? 7. How many moles are in 1.0 x 109 atoms? 8. What is the mass of 1.20 x 1025 atoms of sulfur? 9. How many moles of CO molecules are in 52 g of CO? 10. How many moles of C2H6 are in 124 g? 11. How many moles of CCl4 are there in 56 g? 12. What is the mass of 2.50 mol of H2SO4? 13. What is the mass of 0.25 mol of Fe2O3? 14. How many molecules are there in 52 g of CO? 15. How many formula units are in 22.4 g SnO2? 16. How many molecules are in 116 g CCl4? 17. What is the mass of 3.01 x 1023 formula units of Fe2O3? 18. What is the mass of 1.2 x 1025 molecules of CO? 19. How many O atoms are in 1.25 mol of SO2? 20. How many moles of O atoms do you have when you have 1.20 x 1025 N2O5 molecules? 21. How many formula units are in 5.33 mol of CuCl2? 22. How many copper atoms are in 5.33 mol of CuCl2? 23. How many moles of Cl atoms are in 5.33 mol of CuCl2? 24. How many moles of CuCl2 contain 1.2 x 1023 atoms of Cl? 25. How many O atoms are in 3.15 mol of SnO2? 26. How many H atoms are in 17.5 g (NH4)2C2O4? Answers 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 1.8 mol Na 0.516 mol O 139 g Cu 16 g Fe 4.3 x 1024 Cl atoms 2.7 x 1023 Br atoms 1.7 x 10-15 mol 639 g S 1.9 mol 4.12 mol 0.36 mol 245 g 40. g 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 1.1 x 1024 molecules 8.95 x 1022 formula units 4.54 x 1023 molecules 79.9 g Fe2O3 5.6 x 102 g CO 1.51 x 1024 O atoms 99.7 mol O 3.21 x 1024 formula units 3.21 x 1024 Cu atoms 10.7 mol of Cl atoms 0.10 mol CuCl2 3.79 x 1024 O atoms 6.79 x 1023 H atoms