Chemical Quantities Ch. 7

Sample 1 Dimensional Analysis Calculate the number of seconds in the month of May. (May has 31 days). 31 days  seconds? days  hours  minutes  seconds 31 days x 24 hours x 60 minutes x 60 seconds 1 day 1 hour 1 minute = 2678400 seconds = 2.7 x 106 seconds (2 Sig Figs)

Sample 2 Dimensional Analysis 2) How many kilometers is 6,228 ft? (5280 ft = 1 mile, 0.621 mi = 1 km). ft  km? feet  mile  kilometer 6,228 ft x 1 mi x 1 km = 5280 ft 0.621 mi = 1.899 km

7-1 The Mole

Mole Mole (mol) = SI unit of measure to count numbers of atoms, molecules, or formula units of substances. Avogadro’s constant = the number of “things” (representative particles) in one mol is 6.02 x 1023 1 mol = 6.02 x 1023 representative particles (atoms/molecules/ions/formula units) Ex: there are 6.02 x 1023 carbon atoms in a mol of carbon Ex: there are 6.02 x 1023 eggs in a mol of eggs The mol is good for measuring atoms (small things), NOT macroscopic things.

Representative Particles Substance Rep. Particle Formula Rep. particles in 1 mol Nitrogen Atom N 6.02x1023 Nitrogen gas Molecule N2 Water H2O Calcium ion Ion Ca+2 Calcium fluoride Formula Unit (ionic) CaF2

Mole Road Map (DRAW!) ATOMS/MOLECULES

1) Atoms/Molecules  Moles 6.02 x 1023 Atoms Moles 1 mol = 6.02x1023 atoms Calculation: __ atoms x 1 mol = _____ mol 6.02x1023 atoms Ex: How many moles of Mg is 1.25x1023 atoms of Mg? 1.25x1023atoms Mg x 1 mol Mg = 6.02x1023atoms Mg = 2.08x10-1mol Mg

Practice! How many moles is 2.80x1024 atoms of Si? 2.80x1024atoms Si x 1 mol Si = 6.02x1023atoms Si = 4.65 mol Si

2) Moles  Atoms/Molecules 6.02 x 1023 Moles Atoms 1 mol = 6.02x1023atoms Calculation: __ mol x 6.02x1023 atoms = _____ atoms 1 mol Ex: 4.0 mol P = ? atoms P 4.0 mol P x 6.02x1023 atoms P 1 mol P = 2.4x1024 atoms P

Practice How many molecules is 0.360mol of water? 0.360mol H2O x 6.02x1023molec H2O = 1 mol H2O = 2.17x1023 molecules H2O

HONORS ONLY! 3) Moles  Molecules  Atoms Use when going from moles  atoms for a compound! Calculation: ___ mol x 6.02x1023molecules x __ atoms =__atoms 1 mol 1 molecule Ex: How many atoms are in 2.12 mol of propane (C3H8)? 2.12mol C3H8 x 6.02x1023molec C3H8 x 11 atoms = 1 mol C3H8 1 molec C3H8 =1.40x1025atoms C3H8

HONORS ONLY! Practice! How many atoms are there in 1.14 mol SO3? 1.14mol SO3 x 6.02x1023molec SO3 x 4 atoms = 1 mol SO3 1 molec SO3 = 2.75x1024atoms SO3 How many moles are there in 4.65x1024 molecules of NO2? 4.65x1024 molec NO2 x 1 mol NO2 = 6.02x1023molec NO2 = 7.72 mol NO2

Mole-Mass Relationships 7-2 Part I

Molar Mass Molar Mass = the mass of one mol of a pure substance, expressed in grams. Molar mass (g) = Atomic Mass (amu) on periodic table!! Ex: What is the molar mass of carbon? =12.0g C = 1 mol C Ex: What is the molar mass of hydrogen? =1.0g H = 1 mol H Ex: What is the molar mass of cesium? =132.9g Cs = 1 mol Cs

Molar Mass of a Compound Molar mass of a compound = all of the individual atoms masses combined. Ex: Molar mass of Ethanol C2H6O C = 2 x 12.0g = 24.0g H = 6 x 1.0g = 6.0g O = 1 x 16.0g = 16.0g + 46.0g of Ethanol = 1 mol Ethanol

Practice! What is the molar mass of H2O2? H: 2 x 1.0g = 2.0g O: 2 x 16.0g = 32.0g + 34.0g H2O2 = 1 mol H2O2 What is the molar mass of magnesium hydroxide? Mg(OH)2 Mg: 1 x 24.3g = 24.3g O: 2 x 16.0g = 32.0g H: 2 x 1.0g = 2.0g + 58.3g Mg(OH)2 = 1 mol Mg(OH)2

4) Moles  Mass Molar Mass Moles Mass 1 mol = molar mass (g) Calculation: ___ mol x molar mass(g) = ___ grams 1 mol Ex: How many grams are in 9.45 moles of dinitrogen trioxide? Molar Mass N2O3 = 2x14.0g + 3x16.0g = 76.0g 9.45mol N2O3 x 76.0g N2O3 = ? g 1 mol N2O3 = 718g N2O3

5) Mass  Moles Molar Mass Mass Moles 1 mol = Molar Mass (g) Calculation: ___ mass (g) x 1 mol = ___ mol molar mass(g) Piece of iron (III) oxide is 16.8g. How many moles are in the sample? Molar Mass Fe2O3: 2x55.8g + 3x16.0g = 159.6g 16.8g Fe2O3 x 1 mol Fe2O3 = ? mol 159.6g Fe2O3 = 0.105 mol Fe2O3

Try It! Determine the mass of the following: 3.52 mol of Si 3.52mol Si x 28.1g Si = ? g 1 mol Si =98.9g Si Determine the moles of the following: 1.25g of aspirin, C9H8O Molar mass C9H8O = 9x12.0 + 8x1.0g + 1x16.0g = ? g = 132.0g 1.25g C9H8O x 1 mol C9H8O = 132.0g C9H8O = 0.00947mol C9H8O

6) Mass  Moles  Atoms/ Molecules Molar Mass 6.02 x 1023 Mass Moles Atoms/Molecules 1 mol = Molar Mass (g); 1 mol = 6.02x1023atoms Calculation: Mass(g) x 1 mol x 6.02 x 1023 atoms = atoms molar mass(g) 1 mol 16.8g of Fe into atoms of Fe: 16.8g Fe x 1 mol Fe x 6.02 x 1023 atoms Fe 55.8g Fe 1 mol Fe = 1.81 x 1023 atoms Fe

Try it! Determine the # of atoms in the following: 98.3g of Hg: Mass  Mol  Atom 98.3g x 1 mol x 6.02 x1023 atoms = 200.6g 1 mol = 2.95 x 1023 atoms Hg 45.6g of Au: 45.6g x 1 mol x 6.02 x1023 atoms = 197.0g 1 mol = 1.39 x 1023 atoms Au

Determine the # of grams in the following: Atoms  Mol  Mass 9.33 x 1023atoms Li: 9.33 x 1023atoms Li x 1 mol x 6.9g = 6.02 x1023atoms 1 mol = 10.7g Li 4.757x1023atoms W: 4.757x1023atoms x 1 mol x 183.8g = 6.02 x1023 atoms 1 mol = 145.2g W

Mole-Volume Relationships 7-2 Part II

Molar Volume Standard Temperature and Pressure (STP) = O°C at 1 atmosphere (atm) or 101.3kPa Molar Volume of a gas is the volume that a mole of gas occupies at STP At STP, 1 mol = 22.4L

7) Moles  Volume Molar Volume Moles Volume (Liters) 1 mol = 22.4 L Calculation: ___ mol x 22.4L = ___ L 1 mol What is the volume (L) of 0.60 mol SO2 gas at STP? 0.60mol SO2 x 22.4 L SO2 = ? L 1 mol SO2 = 13 L SO2

8) Volume  Moles Volume (Liters) Moles 1 mol = 22.4 L Calculation: Molar Volume Volume (Liters) Moles 1 mol = 22.4 L Calculation: ___ L x 1 mol = ___ mol 22.4 L How many moles are in 7.2 L of H2O2 at STP? 7.2 L H2O2 x 1 mol H2O2 = ? 22.4 L H2O2 = 0.32mol H2O2

Practice! What is the volume of 3.20x10-3mol CO2 at STP? 3.20x10-3 mol CO2 x 22.4 L CO2 = ? 1 mol CO2 = 0.0717 or 7.17x10-2 L CO2 How many moles are in 5.2 L of H2O at STP? 5.2 L H2O x 1 mol H2O = ? 22.4 L H2O = 0.23 mol H2O

Mole Road Map Mass Atom Mole Volume Molar Mass 1 mol = Avogadro’s # Molar mass (g) Avogadro’s # 1 mol = 6.02x1023 atoms Molar Volume 1 mol = 22.4L Volume

1) 1 mol = _____ L 6.02x1023 Molar mass 22.4 1.0

2) 1 mol = ____ atoms 6.02x1023 Molar mass 22.4 1.0

3) What is the molar mass of C6H12O6? 24.0g 64.0g 180.0g 348.0g

4) How many atoms are in 16g N? Choose correct set-up. 16g x 14.0g x 6.02x1023 atoms = 1 mol 1 mol 16g x 1 mol x 1 mol = 14.0g 6.02x1023 atoms 16g x 14.0g x 1 mol = 1 mol 6.02x1023 atoms 16g x 1 mol x 6.02x1023 atoms = 14.0g 1 mol

Answers C A D