3 How do we measure items?Measure mass in grams.Measure volume in liters.Measure amount in MOLES.
4 We’re not talking about this kind of mole! What is the mole?We’re not talking about this kind of mole!
5 Moles (mol) It is an amount. Defined as the number of carbon atoms in exactly 12 grams of carbon-12.1 mole = 6.02 x of representative particles.6.02 x 1023 is called: Avogadro’s number.1 mole = 6.02 x 1023 = Avogadro’s number
6 Similar Words for amount Dozen:Mole:1 dozen muffins = 12 muffins1 mol muffins = x 1023 muffins2 dozen puppies = 24 puppies2 mol puppies = 1.2 x 1024 puppies36 m&m stuffed donuts = 3 dozen donuts2.4 x 1024 m&m stuffed donuts = 4 mol donuts
7 What are Representative Particles? The smallest pieces of a substance:Changes based on what we’re looking atFor a molecular compound: it is the molecule.For an ionic compound: it is the formula unit (ex: NaCl, MgS).For an element: it is the atom.1 mol of CO2 molecules, 1 mol of NaCl formula units, and 1 mol of H atoms all equal 6.02 x 1023 of that thing.Remember the 7 diatomic elements? (made of molecules)
8 Measuring MolesThe atomic mass on the PT is also the molar mass (g/mol) – mass (in grams) of 1 mole of that atom= 16.0 g/molSince the mole is the number of atoms in 12 grams of carbon-12,Gram atomic mass (GAM)- Equals the mass of 1 mole of an element in grams (from periodic table)12.01 grams of C has the same number of pieces as 1.01 grams of H and grams of Fe.We can write this as:12.01 g C = 1 mole C(this is also the molar mass)(**Remember we can count things by weighing them.)
9 Find the Molar Mass (g/mol) of the following: NitrogenAluminumZinc14.01 g/mol26.98 g/mol65.39 g/mol
10 What about compound mass? In 1 mole of H2O, there are 2 moles of H atoms and 1 mole of O atomsTo find the mass of a compound:Determine number of each element presentMultiply the number times their mass (from the periodic table)Add them up for the total mass
11 Calculating Compound Mass Calculate the mass of magnesium carbonate, MgCO3.24.31 g/mol g/mol x (16.00 g/mol) =84.32 g/mol MgCO3
12 Practice Problem: What is the mass of one mole of CH4? 1 mole of C = g/mol4 mole of H x 1.01 g = 4.04g/mol1 mole CH4 = = g/mol12
13 Mole Practice 1 mol = particles 2.5 mol MgCl2 = ? particles MgCl2 = x 1024 Fe particles = ? mol Fe2.5 mol6.02 x 1023 particles1.5 x 1024 particles of MgCl21 mol7.2 x 1024 particles1 mol12 mol Fe6.02 x particles
14 Molar Mass Practice 47 g/mol 180 g/mol 4. Molar mass of BeF2 = 5. Molar mass of C6H12O6 =Be = 9.0 g/mol(19.0) =47 g/molF = 19.0 g/molC = 12.0 g/mol6(12.0) + 12(1.0) + 6(16.0) =H = 1.0 g/mol180 g/molO= 16.0 g/mol
15 Section 10.2 Mole-Mass and Mole-Volume Relationships
16 Use to make conversion factors from these. Since Molar Mass is…Number of grams in 1 mole.grams per mole (g/mol)Use to make conversion factors from these.- Use molar mass to convert to grams or mols of a substance.
17 For example How many moles is 5.69 g of NaOH? = How many grams in .53 mol of NaOH?.142 mol NaOH1mol NaOH5.69 g NaOH40.0g NaOH40.0g NaOH21.2 g NaOH.53 mol NaOH1mol NaOH17
18 28.1 grams C 1.000 mol Mg Practice Problems: How much would 2.34 moles of carbon weigh?How many moles of magnesium is g of Mg?28.1 grams C1.000 mol Mg
19 The Mole-Volume Relationship Under different circumstances, gases can change.Two things effect the volume of a gas:a) Temperature and b) Pressure**We need to compare all gases at the same temperature and pressure.
20 Standard Temperature and Pressure abbreviated STP0ºC (273K) and 1.0 atm pressureAt STP 1 mole of gas occupies L= molar volume22.4 L/mol of any gas at STP20
21 Practice Problems: = 0.253 mol O2 What is the volume of 4.59 mole of CO2 gas at STP?How many moles is L of O2 at STP?4.59 mol CO222.4 L CO2= 103 L CO21 mol CO25.67 L O21 mol O2= mol O222.4 L O2
22 12.3 L CH4 22.4 L CH4 8.8 g CH4 1 mol CH4 16.0 g CH4 1 mol CH4 What is the volume of 8.8 g of CH4 gas at STP?=22.4 L CH48.8 g CH41 mol CH416.0 g CH41 mol CH412.3 L CH4
23 Summary: These four items are all equal: a) 1 mole b) molar mass (in grams/mol)c) 6.02 x 1023 particles (atoms, molecules, or formula units)d) 22.4 L of a gas at STP**Thus, we can make conversion factors from them.
24 Avog. # Practice problems: How many molecules of CO2 are in 4.6 moles of CO2?How many moles of water is in 5.87 x molecules?How many atoms of carbon are in moles of Carbon?How many moles is 7.78 x 1024 formula units of MgCl2?2.8 x 1024 molecules of CO2mol H2O (or 9.75 x 10-2)7.405 x 1023 atoms C12.9 moles MgCl2
25 Mixed Practice Problems: How many atoms of lithium is 1.0 g of Li?How much would 3.45 x 1022 atoms of U weigh?What is the volume of 10.0 g of CH4 gas at STP?8.7 x 1022 atoms Li13.6 g U14.0 L CH4
26 Section 10.3 Percent Composition and Chemical Formulas
27 Percentage Composition Percentage by mass of each element in a compound
28 Calculating Percent Composition of a Compound Like all percent problems:part wholeFind mass of each element (from the periodic table)Next, divide by total mass of compound; then x 100x 100 % = percent
29 Percentage Composition Find the % composition of Cu2S.g Cug Cu2S%Cu = 100 =79.85% Cu32.07 g Sg Cu2S%S = 100 =20.15% S
30 Percentage Composition Find the mass percentage of water in calcium chloride dihydrate, CaCl2•2H2O?36.04 gg%H2O = 100 =24.51%H2O
31 Empirical Formula (EF) Lowest whole number ratio of atoms in a compoundC2H6simplify subscriptsCH3
32 Empirical Formula (EF) Just find lowest whole number ratioC6H12O6CH4NFormula is not just ratio of atoms, it is also ratio of moles.In 1 mole of CO2 there is 1 mole of carbon and 2 moles of oxygen.In one molecule of CO2 there is 1 atom of C and 2 atoms of O.= CH2O= this is already the lowest ratio.
33 Formulas (continued)Formulas for ionic compounds are ALWAYS empirical (the lowest whole number ratio = cannot be reduced).*Remember, we simplify beforehandExamples:NaClMgCl2Al2(SO4)3K2CO3
34 Formulas (continued)Formulas for molecular compounds MIGHT be empirical (lowest whole number ratio).Molecular:H2OC6H12O6C12H22O11(Correct formula)Empirical:H2OCH2OC12H22O11(Lowest whole number ratio)
35 FormulasEmpirical Formula (EF) = lowest whole number ratio of elements in a compound.Molecular Formula (MF) = the actual ratio of elements in a compound.The two can be the same.CH2 = C2H4 =C3H6 = H2O =H2O is also MFEFMFMFEF35
36 Last extra practice slide How many O atoms are in 5 mol of Al2O3?How many Al atoms are in 5 mol of Al2O3?mol O6.02e23atoms O5 mol Al2O331mol Al2O31mol O9.03e24 atoms O5 mol Al2O32 mol Al6.02e23 atoms Al1 mol Al2O31 mol Al6.02e24 atoms Al