Calculating Molar Mass

What is a Mole? - - The mole is a counting unit (similar to a dozen) o Except instead of 12, it’s 602 billion trillion 602,000,000,000,000,000,000,000 o It is commonly written as: 6.02 X 1023 (in scientific notation) The mole works just like other counting units 1 mole of cookies = 6.02 X 1023 cookies o 1 dozen cookies = 12 cookies o o - 1 dozen cars = 12 cars 1 pair of shoes = 2 shoes 1 mole of cars = 6.02 X 1023 cars 23 1 mole of shoes = 6.02 X 10 cars This number is named in honor of Amedeo AVOGADRO (born 1776 – died 1856), who studied quantities of gases and discovered that no matter what the gas was, there were the same number of molecules present o So 6.02 x 1023 is known as Avogadro’s Number Learning Check – please circle the correct answer 1. How many sulfur atoms are in a mole of sulfur atoms? a. 12 atoms b. 602 atoms c. 6.02 x 1023 atoms d. 6.02 x 1012 atoms 2. Suppose we invented a new collection unit called a rapp. One rapp contains 8 objects. How many oranges are in 2.0 rapps? a. 8 oranges b. 12 oranges c. 16 oranges d. 6.02 x 1023 oranges The coolest thing about the mole: you can find the mass of 1 mole of an atom by looking up its atomic mass from the periodic table! The mass of a mole of any compound is equivalent to the sum of the atomic masses of the elements that make up that compound! This means: 1 mole of atoms is 6.02 x 1023 atoms and has a mass of that atom’s atomic mass! Calculating Molar Mass How to calculate Molar mass: 1. Look at the chemical formula of the compound 2. Find the Atomic Mass for each element (there is a periodic table on the last page of this packet!) 3. Add the totals together 4. Round to the nearest 0.01 place Example 1: Example 2: Find the Molar Mass of SO3 Find the Molar Mass of Ba(NO3)2 1 S atom x 32.066 = 32.066 g/mol 3 O atoms x 15.999 = 47.997 g/mol 1 Ba atom x 137.327= 137.327 g/mol 2 N atoms x 14.007 = 28.014 g/mol 6 O atoms x 15.999=95.994 g/mol 32.066 g/mol + 47.997 g/mol =80. 063 g/mol The molar mass of SO3 is 80.06 g/mol 137.327 g/mol + 28.014 g/mol + 95.994 g/mol = 261.335 g/mol The molar mass of Ba(NO3)2 is 261.34 g/mol Calculate the molar mass and mass of 1 mole of each compound. Show you work and don’t forget units. Molar mass is in grams/mole. Mass is in grams. 1. N2 Molar mass of N2 ____________. 1 mole of N2 has a mass of ____________. 2. H2O Molar mass of H2O ____________. 1 mole of H2O has a mass of ____________. 3. CuCl2 4. C6H12O6 Molar mass of C6H12O6 ____________. 1 mole of C6H12O6 has a mass of ____________. 5. CaCO3 Molar mass of CaCO3 ____________. 1 mole of CaCO3 has a mass of ____________. 6. (NH4)2O Molar mass of (NH4)2O is ____________ 1 mole of (NH4)2O has a mass of ____________. Molar mass of CuCl2 ____________. 1 mole of CuCl2 has a mass of ____________. Moles and Mass Wrap Up If you need additional space, show work on a separate page and turn in your work with your packet. Part 1: Reviewing the mole 1. If I have “one mole” of atoms, how many atoms do I have? 2. If I have 3 moles of donuts, how many donuts do I have? 3. If I have ½ a mole of carbon, how many carbon atoms do I have? Part 2: Molar Mass Calculate the molar mass of each of the following. You must show all of your work to get credit for these problems. “I just did it in my calculator” is not an acceptable response. A periodic table is included as the last page of this packet!!! 4. KF 5. H2S 6. NaNO3 7. Mg(OH)2 8. Al2(SO4)3 Part 3: Using Molar Mass Use the molar masses you calculated in part 2 above to answer the following questions. The table below shows an example problem. You must show all of your work to get credit for these problems. “I just did it in my calculator” is not an acceptable response. Example: If I have 1 mole of KF, how much will it weigh? How many molecules will it be? What about 2 moles? Moles KF 1 mole KF 2 moles KF Mass/Weight 58.096 grams 2 x 58.096 = 116.192 grams Molecules 6.02 x 1023 molecules 2 x (6.02 x 1023) = 12.04 x 1023 molecules 9. How much will 1 mole of H2S weigh? 10. How much will 0.50 moles of NaNO3 weigh? 11. How much will 3 moles of Mg(OH)2 weigh? 12. If I have about 68.2 grams of H2S, how many moles do I have? 13. If I have about 342.15 grams of Al2(SO4)3, how many molecules do I have? Answer Keys 5.1 1) 6.02 x 10 23 atoms 2) 16 oranges 5.2 1. N2 Molar mass of N2 ______28.01 g/mol______. 1 mole of N2 has a mass of _____28.01g_______. 2. H2O Molar mass of H2O _______18.02g/mol_____. 1 mole of H2O has a mass of _____18.02g _______. 3. CuCl2 Molar mass of CuCl2 ____134.45g/mol________. 1 mole of CuCl2 has a mass of ____134.45g________. 4. C6H12O6 Molar mass of C6H12O6 _____180.16g/mol_______. 1 mole of C6H12O6 has a mass of _____180.16g_______. 5. CaCO3 Molar mass of CaCO3 ___100.09g/mol_________. 1 mole of CaCO3 has a mass of ___100.09g_________. 6. (NH4)2O Molar mass of (NH4)2O is __52.08g/mol__________ 1 mole of (NH4)2O has a mass of ____52.08g________. 5.3 Part 1 1. If I have “one mole” of atoms, how many atoms do I have? 6.02 x 10 23 atoms 2. If I have 3 moles of donuts, how many donuts do I have? 3 x 6.02 x 10 23 atoms = 1.81 x 1024donuts 3. If I have ½ a mole of carbon, how many carbon atoms do I have? 6.02 x 1023 atoms / 2 = 3.01 x 1023 carbon atoms Part 2 4. KF = 58.10 g/mol 5. H2S =34.10 g/mol 6. NaNO3 = 84.99 g/mol 7. Mg(OH)2 = 58.32 g/mol 8. Al2(SO4)3 =342.15g/mol Part 3 9. How much will 1 mole of H2S weigh? 34.10 g 10. How much will 0.50 moles of NaNO3 weigh? 42.50 g 11. How much will 3 moles of Mg(OH)2 weigh? 174.96 g 12. If I have about 68.2 grams of H2S, how many moles do I have? 2 moles (2.00 mols with sigfigs!) 13. If I have about 342.15 grams of Al2(SO4)3, how many molecules do I have? 6.02 x 1023 molecule 14. Periodic Table of Elements 1 18 1 2 H He Hydrogen 2 1.008 3 13 4 Li Lithium 6.941 11 6 Be Key: Beryllium 9.012 5 Atomic Number C Symbol 6 B Name 12.01 Average Atomic Mass Carbon Boron 10.81 12 14 13 15 7 C Carbon 12.01 14 16 8 N Nitrogen 14.01 15 17 9 O Helium 4.003 10 F Ne Oxygen Fluorine 16.00 19.00 20.18 16 17 Neon 18 Na Mg Al Si P S Cl Ar Sodium Magnesium Aluminum Silicon Phosphorus Sulfur Chlorine Argon 22.99 19 K Potassium 39.10 37 Rb 24.31 20 Ca Calcium 40.08 38 Sr Rubidium Strontium 85.47 87.62 55 56 3 21 Sc Scandium 44.96 39 Y Yttrium 88.91 57 4 22 Ti Titanium 47.88 40 Zr Zirconium 91.22 72 5 23 V 6 24 25 8 26 Vanadium Chromium Manganese Mn Fe 50.94 52.00 54.94 55.85 41 Nb Niobium 92.91 73 Cr 7 42 Mo Molybdenum 95.94 74 43 Iron 44 Ru Technetium Ruthenium (98) 75 101.1 76 9 27 Co 10 28 29 12 30 Cobalt Nickel Copper Cu Zn 58.93 58.69 63.55 65.41 45 Rh Rhodium 102.9 77 Ni 11 46 47 Pd Ag 106.4 107.9 Palladium 78 Silver 79 Zinc 48 Cd Cadmium 112.4 80 26.98 31 Ga Gallium 69.72 49 28.09 32 Ge Germanium 72.59 50 In Sn 114.8 118.7 Indium 81 Tin 82 30.97 33 As Arsenic 74.92 51 Sb Antimony 121.8 83 32.07 34 Se Selenium 78.96 52 Te Tellurium 127.6 84 35.45 39.95 35 Br Bromine 53 I Iodine 85 Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine 132.9 137.3 190.2 192.2 87 Fr Francium (223) 88 Ra Radium 226 89 Ac Actinium (227) 104 Rutherfordium (261) 180.9 105 Dubnium (262) 183.9 106 Seaborgium (266) 186.2 107 Bohrium (264) 108 Hassium (277) 109 195.1 110 197.0 111 200.6 112 Meitnerium Darmstadtiu Roentgeniu Ununbium m m (268) (269) (272) (277) 204.4 113 207.2 114 209.0 115 Ununtrium Ununquadiu Ununpentiu m m (284) (289) (288) (209) 112 Ununhexiu m 54 Xe Xenon 126.9 131.3 Cs 178.5 Kr Krypton 79.90 83.80 Cesium 138.9 36 (210) 86 Rn Radon (222)