2Tuesday, April 5th: “A” Day Wednesday, April 6th: “B” Day Agenda PSAE Practice Test #3Begin Chapter 7: “The Mole and Chemical Composition”In-Class Assignments:Practice pg. 228: #1-4Practice pg. 229: #1-4Concept Review: “Avogadro’sNumber and Molar Conversions”: #1-5
3Begin Section 7.1: “Avogadro’s Number and Molar Conversions” Atoms, ions, and molecules are very small, so even tiny samples have huge numbers of particles.Scientists use the mole to make counting such large numbers easier.Mole: the SI unit for amount; the number of atoms in exactly 12 grams of carbon-12.
4Avogadro’s Number & the Mole The number of particles in a mole is called Avogadro’s Number.Avogadro’s number is 1023; the number of atoms or molecules in 1 mole
5The Mole is a Counting Unit The mole is used to count out a given number of particles, whether they are atoms, molecules, formula units, ions, or electrons.The mole is just one kind of counting unit:1 dozen = 12 objects1 roll = 50 pennies1 hour = 3,600 seconds1 pair = 21 mole = 1023 particles
6Conversion Factors The definition of one mole is: 6.022 1023 particles = 1 molUsing this definition, we get 2 conversion factors:6.022 X 1023 particles = 11 mol_____1 mol________ = 16.022 X 1023 particles
7Choose the Conversion Factor that Cancels the Known Units **Because a conversion factor is equal to 1, it can multiply any quantity without changing the value. Only the units are changed. **When solving conversion problems, the unit that you’re trying to get rid of goes on the bottom of the fraction.
8Converting Between Amount in Moles and Number of Particles
9Find the number of molecules in 2.5 mol of sulfur dioxide, SO2. Sample Problem A, pg 228 Converting Between Amount in Moles to Number of ParticlesFind the number of molecules in 2.5 mol of sulfur dioxide, SO2.Known: 2.5 moles of SO2Unknown: # of molecules of SO2Conversion factor: X 1023 molecules SO21 mole SO2Start with what you know, mult. by conversion factor:2.5 mol SO2 X X 1023 molecules SO2 = 1.5 X mole SO molecules SO2
10Additional PracticeHow many particles are there in 2.45 X 10-6 mol of nickel, Ni (II) selenide, NiSe?Known: X 10-6 moles NiSeUnknown: # of particles of NiSeConversion factor: X 1023 particles NiSe1 mol NiSeStart with what you know, mult. by conversion factor:2.45 X mol NiSe X X 1023 particles NiSe = mole NiSe1.48 X 1018 particles NiSe
11We can go the other way too and convert number of particles to amount in moles…
12Sample Problem B, pg. 229 Converting Number of Particles to Amount in Moles A sample contains 3.01 X 1023 molecules of sulfur dioxide, SO2. Determine the amount in moles.Known: X 1023 molecules of SO2Unknown: moles of SO2Conversion factor: ____1 mole SO2_____6.022 X 1023 molecules SO2Start with what you know, mult. by conversion factor:3.01 X 1023 molecules SO2 X __1 mole SO2______= moles SO2
13Additional PracticeHow many moles are equivalent to 7.95 X 1024 copper (II) chloride, CuCl2, formula units?Known: X 1024 CuCl2 formula unitsUnknown: # of moles of CuCl2 formula unitsConversion factor: _____1 mole CuCl2__6.022 X 1023 formula units CuCl2Start with what you know, mult. by conversion factor:7.95 X form. unit CuCl2 X ____1 mole_CuCl2___6.022 X 1023 form. unit CuCl2= 13.2 mol CuCl2
14In-Class Assignments You must SHOW WORK! Practice pg. 228: #1-4Practice pg. 229: #1-4Concept Review: Avogadro’s Number and Molar Conversions”: #1-5