Slide 1 / 158 Slide 2 / 158 Mole Calculations Slide 3 / 158 Slide 4 / 158 Table of Contents Avogadro's Number Click on the topic to go to that section · Avogadro's Number · Molar Mass · Molar Volume · Percent Composition · Emperical Formula Return to Table of Contents Slide 5 / 158 Slide 6 / 158 Atomic Mass Atomic Mass Recall an atom's atomic mass is equal to the number of protons plus the number of neutrons in the atom. What if you wanted to measure the mass of one atom in the laboratory? Would it be possible? Atomic Number 6 or number of protons (Z) C Average 12.01 Atomic Mass in amu The unit for atomic mass is amu. A single atom has a very small mass. Carbon-12 has 6 protons and 6 neutrons. One carbon atom has a mass of about 2.0 x 10 -23 grams . One amu is equal to 1/12 the mass of carbon-12 or approximately the mass of one proton or neutron mass of 1 proton = 1 amu mass of 1 neutron = 1 amu
Slide 7 / 158 Slide 8 / 158 The Mole Calculating Avogadro's Number The atomic mass of one carbon atom is 12.01 amu or 2x10 -23 g. It takes a lot of atoms to give us enough material to directly measure in a lab. How many carbon atoms would it take to get 12.01 grams of carbon? Hydrogen has a mass of 1 amu. How many atoms of hydrogen would be needed to make a 1 gram sample of hydrogen? Givens: mass of 1 carbon atom = 2x10 -23 g 602,200,000,000,000,000,000,000 total mass of carbon atoms = 12.01 g The amount 6.02x10 23 is called Avogadro's number or a mole . 2x10 -23 g x ? of atoms = 12.01 g ? of atoms 12.01 g = How big is a mole? 2x10 -23 g ? of atoms = 6.02 x 10 23 atoms Slide 9 / 158 Slide 10 / 158 Holy Mole-y! The Mole 1 mole of pennies could One mole of marbles would cover the A mole is just a grouping of numbers...like dozen, ream, etc. entire Earth (oceans included) for a be distributed to all the depth of two miles! currently-living people of A dozen means 12 of something. the world so that they A mole means 6.02 x 10 23 of something. could spend a million dollars per hour every hour (day and night) for Common Grouping Quantities the rest of their lives! 1 dozen = 12 1 gross =144 If you were able to count at the rate of 1 million numbers a second, it 1 ream = 500 would take about 20 billion years to count out one mole! 1 mole = 6.02 x 10 23 Slide 11 / 158 Slide 12 / 158 2 How many eggs are in half a dozen eggs? 1 How many eggs are in two dozen eggs? 12 A A 12 24 B 24 B C 0.0833 C 6 D 2 D 0.5 6.02 x 10 23 E 6.02 x 10 23 E
Slide 13 / 158 Slide 14 / 158 4 How many pieces of gold dust are in 2 moles of 3 How many particles of sand are in 0.5 moles of gold dust? sand? A 1.5 x 10 23 A 1.5 x 10 23 B 3.01 x 10 23 B 3.01 x 10 23 C 6.02 x 10 23 C 6.02 x 10 23 D 1.2 x 10 24 D 1.2 x 10 24 E 6.02 x 10 24 E 6.02 x 10 24 1 mole = 6.02 x 10 23 1 mole = 6.02 x 10 23 Slide 15 / 158 Slide 16 / 158 6 How many dozen eggs are in a container of 18 5 How many dozen eggs are in a container of 6 eggs? eggs? 1.5 A A 4 B 3 B 0.5 C 0.67 C 1 D 2 D 2 6.02 x 10 23 E 6.02 x 10 23 E Slide 17 / 158 Slide 18 / 158 Dimensional Analysis Dimensional Analysis How many eggs are in 47 dozen eggs? How many eggs are in 47 dozen eggs? To solve the above problem: The number 47 makes this question a bit more difficult to calculate mentally. 1. Choose the equality with the correct dimensions or units: In chemistry, it is common practice to use equalities and 1 dozen eggs = 12 eggs dimensional analysis to solve problems. 2. Turn the equality into a fraction. Equalities are two quantities that are identical in value but use Since 1 dozen and 12 are equal quantities 1 dozen = 12 different units. Examples of equalities include: can also be written as a fraction: 1 dozen = 12 1 dozen eggs 12 eggs 1 mole = 6.02x10 23 = = 1 = 1 meter = 1000 millimeters 12 eggs 1 dozen eggs 1 hour = 60 minutes
Slide 19 / 158 Slide 20 / 158 7 The Milky Way Galaxy may have up to 400 billion Dimensional Analysis (4 x 10 14 stars). How many moles of stars does it How many eggs are in 47 dozen eggs? have? 3. Start with your given: A 1.5 x 10 9 47 dozen B 6.7 x 10 -10 Use dimensional analysis ! Choose the fraction that has the appropriate dimensions or units to convert from your given dimensions to your unknown dimensions. C 10 unknown dimension 12 eggs 1 dozen D is in the numerator 0.5 or 12 eggs 1 dozen 6.02 x 10 23 E 4. Multiply your given by your chosen fraction and cancel out the units: 1 mole of stars = 6.02 x 10 23 stars 47 dozen x 12 eggs = 564 eggs 6.02 x 10 23 stars 1 mole of stars or 1 dozen 6.02 x 10 23 stars 1 mole of stars Slide 21 / 158 Slide 22 / 158 8 Mathematicians estimate Earth's beaches Measuring Matter with Moles contain nearly 5.6 x 10 21 grains of sand. How many moles of sand are on Earth's beaches? The mole is the SI unit for measuring the amount of particles in a chemical substance. 1.5 A One mole (mol) of a substance is 6.02 x 10 23 representative particles of that substance. B 9.3 x 10 -3 C 10.0 D 107.5 6.02 x 10 23 E 1 mole of Carbon 1 mole = 6.02 x 10 23 Slide 23 / 158 Slide 24 / 158 9 How many atoms of titanium are in a sample Measuring Matter with Moles containing 0.5 mole of titanium? How many moles of Gold are there in a sample containing 3.01 x 10 23 atoms of Gold? 1.5 x 10 23 A 1 mol = 6.02 x10 23 atoms B 3.01 x 10 23 Given quantity: 3.01 x 10 23 Au atoms C 6.02 x 10 23 1 mol Au 6.02 x10 23 Au atoms D 1.2 x 10 24 or Equalities: 6.02 x10 23 Au atoms 1 mol Au E 6.02 x 10 24 Solve and cancel units: 1 mol = 6.02 x 10 23 1 mol Au 3.01 x 10 23 Au atoms x = 0.5 mol Au 6.02 x10 23 Au atoms
Slide 25 / 158 Slide 26 / 158 10How many atoms of sodium are in a sample 11 How many moles of potassium are in a sample containing 2.0 moles of sodium? containing 3.01 x 10 23 atoms of potassium? A 1.0 A 1.5 x 10 23 B 2.0 B 3.01 x 10 23 C 0.5 C 6.02 x 10 23 D 0.75 D 1.2 x 10 24 6.02 x 10 24 E 6.02 x 10 22 E 1 mol = 6.02 x 10 23 1 mol = 6.02 x 10 23 Slide 27 / 158 Slide 28 / 158 13 How many moles of tungsten atoms are there in a 12 How many moles of potassium are in a sample sample containing 1.8 x 10 24 atoms of tungsten? containing 1.2 x 10 24 atoms of potassium? A 0.33 mol A 0.25 mol B 0.50 mol B 0.50 mol C 1.0 mol C 1.0 mol D 2.0 mol D 1.5 mol E 3.0 mol E 3.0 mol 1 mol = 6.02 x 10 23 1 mol = 6.02 x 10 23 Slide 29 / 158 Slide 30 / 158 14 How many moles of silver are there in a pure 15 How many atoms are there in 5.00 mol of hafnium? sample containing 1.5 x 10 23 atoms of silver? A 6.02 x10 23 atoms A 0.10 mol 1.20 x 10 23 atoms B 0.25 mol B 1.20 x 10 22 atoms C C 0.50 mol D 3.43 x 10 23 atoms D 1.0 mol E 3.01 x 10 24 atoms E 1.5 mol 1 mol = 6.02 x 10 23 1 mol = 6.02 x 10 23
Slide 31 / 158 Slide 32 / 158 Measuring Matter with Moles Measuring Matter with Moles laboratory sample size A mole of ANY substance contains Avogadro’s number of molecule of H 2 O representative particles, or 6.02 x 10 23 representative particles. H Avagadro's O number of H 1 mole of C atoms = 6.02 X 10 23 atoms of C molecules 18.0 amu (6.02 x10 23 ) 1 mol H 2 O 1 mole of bicycles = 6.02 x 10 23 bicycles (18.0 g) In 1 mole of carbon there are 6.02 x 10 23 carbon atoms. The term representative particle refers to the species or types of particles in the substance In 1 mole of water there are 6.02 x 10 23 water molecules. For Example: In 1 mole of NaCl there are 6.02 x 10 23 formula units. atoms, molecules, formula units, ions Slide 33 / 158 Slide 34 / 158 16 Formula units refer to particles of __________ 17 How many molecules are there in 2.10 mol CO 2 ? compounds and molecules refer to particles of A 3.79 x 10 24 __________ compounds. B 3.49 x 10 -24 A molecular/covalent, ionic C 1.05 x 10 -23 B ionic, molecular/covalent D 2.53 x 10 24 C atoms, molecular E 1.26 x 10 24 D atoms, ionic E ionic, atomic 1 mol CO 2 = 6.02 x 10 23 CO 2 molecules Slide 35 / 158 Slide 36 / 158 18 How many moles of helium atoms are there in a 19 How many moles of NaCl are there in a pure pure sample containing 6.02 x 10 24 atoms of sample containing 6.02 x 10 23 formula units of helium? sodium chloride, NaCl? A 2.0 mol A 1.0 mol B B 2.0 mol 4.0 mol C 6.0 mol C 4.0 mol D 6.0 mol D 10.0 mol 6.02 x 10 23 mol E E 2.4 x 10 24 mol 1 mol NaCl = 6.02 x 10 23 NaCl formula units 1 mol He = 6.02 x 10 23 He atoms
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