Mole Unit with answers

Chemistry 11 INTRODUCTION TO UNIT TWO THE MOLE TODAY IS A VERY SPECIAL DAY IN CHEMISTRY! October 23 Celebrated by chemists annually from 6.02 am to 6.02 pm on October 23rd, Mole Day commemorates Avogadro’s number (6.022140857 × 1023), which is the number of atoms in exactly 12 grams of carbon-12 (one mole). This was founded by the National Mole Day Foundation on May 15th 1991. What is a dozen? Consider this: the mass of 12 donuts does not equal the mass of 12 timbits OR: If you are offered 1500 g donuts vs. 1500 g timbits (for free!), which would you take? You will need a lot more timbits to reach 1500 g 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 to 3 significant figures is 6.02 x 1023 (This is the number that represents one mole, and it is called “Avogadro's number”) The History of the Term "Mole" The Avogadro constant is named after the early nineteenth century Italian scientist Amedeo Avogadro, who is credited (in 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, 6.02 x 1023, in honor of Avogadro. Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto 9 August 1776, Turin – 9 July 1856 PUTTING AVOGADRO’s “mole” into the context of the periodic table: example: B5 (atomic number 5) The mass of one Boron atom is 10.8 amu amu stands for “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 (one mole) of Boron will have a mass of 10.8 g. 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) Another example: The ionic compound, Calcium Sulphide. Chemical Formula CaS. If we wanted to talk about one molecule of calcium sulphide, we would say 1 Ca atom = 40.1 amu and 1 sulphur atom = 32.1 amu BUT, it is much more practical to talk about 1 mole of CaS molecules 1 mole calcium = 40.1 g 1 mole sulphur = 32.1 g That’s 6.02 x 1023 calcium atoms and 6.02 x 1023 sulphur atoms, making 6.02 x 1023 CaS molecules) with a total mass of 72.1 g. So we would say that the molar mass of CaS is 72.1 g/mole. molar mass can also stated as molecular mass. 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!!!! DO YOU THINK YOU HAVE A GRASP OF WHAT ‘the mole” is? COUNTING ATOMS Complete the following table. Molecular formula Name water # of Molecules indicated 1 # of each atom in the given molecular formula 2H 1O H2 O Silver carbonate 1 2Ag 1C 3O CuSO4 1 Copper (II) nitrate 1 Ammonium sulphide 1 chlorine gas 4 liquid nitrogen 3 solid iodine 2 Zinc acetate 1 Magnesium Phosphate 2 7 LiH2PO4 K4P2O7 • 3 H2O Potassium Pyrophosphate trihydrate Aluminum Oxide Dihydrate 6 SnCl2 • 5 H2O 1 Determine the molar mass of each of the following: (note that we can also call it atomic mass or molecular mass, depending on whether we are talking specifically about an atom or a molecule) SUBSTANCE MOLAR MASS Cu 63.546 g / mole Sn H2O Copper (II) sulphate 1 mole Cu, 1 mole S, 4 moles O, but only 1 mole CuSO4 !!! Oxygen gas Bromine liquid Solid Phosphorus crystals Copper (I) phosphide potassium chromate ammonium oxalite Copper (II) nitrate Aluminum Oxide Dihydrate COUNTING ATOMS ANSWER KEY Molecular formula Name # of Molecules # of each atom H2O water 1 2H Ag2CO3 Silver carbonate 1 2Ag 1C 3 O CuSO4 Copper (II) sulphate 1 I Cu 1S 4 O Cu(NO3)2 Copper (II) nitrate 1 I Cu 2N 6 O (NH4)2S Ammonium sulphide 1 2N 8H 1S 4 Cl2 chlorine 4 8 Cl 3 6N solid iodine 2 4I Zn(CH3COO)2 Zinc acetate 1 2 Mg3(PO4)2 Magnesium Phosphate 2 1 Zn 4 C 6H 4 O 6 Mg 4 P 16 O 7 Li 14 H 7 P 28 O 4 K 2P ten O 6 H 2 Al 5 O 4 H 6 Sn 12 Cl 60 H 30 O (g) 1O (is a gas at room temp) 3 N2 (l) nitrogen o (is a liquid at - 210 C, and a gas at temps above -196oC) 2 I2 (s) 7 LiH2PO4 Lithium dihydrogen phosphate K4P2O7 • 3 H2O Potassium Pyrophosphate trihydrate Al2O3 • 2 H2O Aluminum Oxide Dihydrate 6 SnCl2 •5 H2O Tin (II) chloride pentahydrate 7 1 1 6 Determine the molar mass of each of the following: SUBSTANCE MOLAR MASS Cu 63.546 g / mole Sn 118.711 g / mole H2O 18.015 g / mole Copper (II) sulphate 159.608 g / mole 1 mole Cu, 1 mole S, 4 moles O, but only 1 mole CuSO4 !!! Oxygen gas O2 31.998 g / mole Bromine liquid Br2 159.808 g / mole Solid Phosphorus crystals P4 123.896 g / mole Copper (I) phosphide 221.612 g/ mole Cu3P potassium chromate K2CrO4 194.188 g / mole ammonium oxalite (NH4)2C2O3 108.097 g/ mole Copper (II) nitrate Cu(NO3)2 187.553 g / mole Aluminum Oxide Dihydrate 137.991 g / mole Al2O3 • 2 H2O