Presentation on theme: "Chapter 10 Chemical Quantities"— Presentation transcript:
1 Chapter 10 Chemical Quantities Hingham High SchoolMr. Clune
2 What is a Mole?You can measure mass,or volume,or you can count pieces.We measure mass in grams.We measure volume in liters.We count pieces in MOLES.
3 Moles (abbreviated: mol) Defined as the number of carbon atoms in exactly 12 grams of carbon-12.1 mole is 6.02 x particles.Treat it like a very large dozen6.02 x is called Avogadro’s number.
4 Representative particles The smallest pieces of a substance.For a molecular compound: it is the molecule.For an ionic compound: it is the formula unit (ions).For an element: it is the atom.Remember the 7 diatomic elements (made of molecules)
5 Types of questions 5 17 3 2 5 How many oxygen atoms in the following? CaCO3Al2(SO4)3How many ions in the following?CaCl2NaOH517325
6 Measuring Moles Remember relative atomic mass? The amu was one twelfth the mass of a carbon-12 atom.Since the mole is the number of atoms in 12 grams of carbon-12,The decimal number on the periodic table is also the mass of 1 mole of those atoms in grams.
7 Molar Mass Equals the mass of 1 mole of an element in grams 12.01 grams of C has the same number of pieces as grams of H and grams of iron.We can write this as g C = 1 mole CWe can count things by weighing them.
8 X = 28.10g Examples How much would 2.34 moles of carbon weigh? 1 mole of C is 12.01g or12.01 g/mole2.34 moleXgmole=28.10g
9 X = Examples How many moles of magnesium is 24.31 g of Mg? 1 mole of Mg is 24.31g or24.31 g/mole1 mole24.31 g24.31gX=1 mole
10 8.67x1022atoms Examples How many atoms of lithium is 1.00 g of Li? 6.94g/mole6.02x1023 atomsmole1.00g1 mole6.94g6.02x1023 atomsmoleXX8.67x1022atoms
11 13.6g How much would 3.45 x 1022 atoms of U weigh? 238.03g/mole 6.02x1023atm3.45x1022atm238.03gmoleXX13.6g
12 What about compounds? To find the mass of one mole of a compound determine the moles of the elements they haveFind out how much they would weighadd them up
13 What about compounds?H2O1 mole of H2O molecules has two moles of H atoms and 1 mole of O atoms
14 H2O What about compounds? H:2 moles X 1.08g/mole = 2.16g O:1 mole X 16.00g/mole= g+1 mole of H20 = g
15 What is the mass of one mole of CH4? What about compounds?What is the mass of one mole of CH4?1 mole of C x g = 12.02g4 mole of H x g = g+1 mole CH4 = 16.05g
16 What about compounds? The Molar Mass of CH4 is 16.05g this is the mass of one mole of a molecular compound.
17 Moles to Mass Conversions How many grams of Na are there in 1.23 moles?1. How many grams of Na are there in 1 mole?22.99g/mol2. How many grams of Na are there in 1.23 moles?1.23 molg molX28.28g=
18 Moles to Mass Conversions How many grams of C6H12O6 are there in 0.56 moles?1. How many grams of C6H12O6 are there in 1 mole?C: 6 x 12.01g = gH: 12 x 1.01g = gO: 6 x 16.00g = g+180.18g/mol
19 Moles to Mass Conversions 2. How many grams of C6H12O6 are there in 0.56 moles?0.56molg molX28.28g=
20 Representative Particles MolesHow many moles of water is 5.87 x molecules?1 mole6.02 x 1023molecules5.87 x 1022moleculesX=0.098 moles or 9.8 x 10-2 moles
21 How many molecules of CO2 are there in 4.56 moles of CO2 ? 6.02 x 1023molecules1 mol4.56 mol=X2.75 x 1024 molecules
22 How many atoms of carbon are there in 1.23 moles of C6H12O6 ? 6.02 x 1023molecules1 mol1.23 mol=X7.40 x 1023molecule6 atoms of C1 moleculeX=4.44 x 1024 atoms of C
23 How many moles is 7.78 x 1024 formula units of MgCl2? 6.02 x 1023molecules7.78 x 1024moleculesX=12.92 moles
24 5.00 moles What is the weight of 3.01 x 1024 molecules of NaOH? 1. Find the number of moles.1 mole6.02 x 1023molecules3.01 x 1024moleculesX=5.00 moles
25 2. Find the mass of one mole of NaOH.Na : 1 x = 22.99gO : 1 x = 16.00gH : 1 x = g+40.07g
26 3. Find the mass of 5 molesof NaOH.40.07g1 mol200.35g5 mol=X
27 Practice Problems Worksheet Homework 10-1Practice Problems Worksheet1-16Due: 01/10/05
28 Molar MassMolar mass is the generic term for the mass of one mole of any substance (in grams)The same as: 1) gram molecular mass, 2) gram formula mass, and 3) gram atomic mass- just a much broader term.
29 ExamplesCalculate the molar mass of the following and tell what type it is:Na2SN2O4CCa(NO3)2C6H12O6(NH4)3PO4
30 Molar Mass The number of grams of 1 mole of atoms, ions, or molecules. We can make conversion factors from these.To change grams of a compound to moles of a compound.
33 For example How many moles is 5.69 g of NaOH? need to change grams to moles
34 For example How many moles is 5.69 g of NaOH? need to change grams to molesfor NaOH
35 For example How many moles is 5.69 g of NaOH? need to change grams to molesfor NaOH1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g
36 For example How many moles is 5.69 g of NaOH? need to change grams to molesfor NaOH1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g1 mole NaOH = g
37 For example How many moles is 5.69 g of NaOH? need to change grams to molesfor NaOH1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g1 mole NaOH = g
38 For example How many moles is 5.69 g of NaOH? need to change grams to molesfor NaOH1mole Na = 22.99g 1 mol O = g 1 mole of H = 1.01 g1 mole NaOH = g
39 Gases Many of the chemicals we deal with are gases. They are difficult to weigh.Need to know how many moles of gas we have.Two things effect the volume of a gasTemperature and pressureWe need to compare them at the same temperature and pressure.
40 Standard Temperature and Pressure 0ºC and 1 atm pressureabbreviated STPAt STP 1 mole of gas occupies 22.4 LCalled the molar volume1 mole = 22.4 L of any gas at STP
41 ExamplesWhat is the volume of 4.59 mole of CO2 gas at STP?4.59 mol22.4 L1 molX=L
42 How many moles is 5.67 L of O2 at STP? ExamplesHow many moles is L of O2 at STP?5.67 L1 mol22.4 LX=0.25 mol
43 0.55 mol What is the volume of 8.8 g of CH4 gas at STP? 1. Find the molar mass of CH4.C: 1 X = 12.01gH: 4 X = g+16.05g2. Find the number of moles.8.8g1 mol16.05g=0.55 molX
44 What is the volume of 8.8 g of CH4 gas at STP? 3. Find the volume of CH4.22.4 L1 mol0.55 molX=12.32 L
45 Mole Volume Mass Particle 22.4L 1 mol 22.4L 1 mol molar mass 6.02X1023part.1 molMolemolar mass1 mol6.02X1023part.1 mol1 molmolar massMassParticle
47 Density of a gasD = m / Vfor a gas the units will be g / LWe can determine the density of any gas at STP if we know its formula.To find the density we need the mass and the volume.If you assume you have 1 mole, then the mass is the molar mass (from PT)At STP the volume is 22.4 L.
48 Examples Find the density of CO2 at STP. Find the density of CH4 at STP.
49 The other wayGiven the density, we can find the molar mass of the gas.Again, pretend you have 1 mole at STP, so V = 22.4 L.m = D x Vm is the mass of 1 mole, since you have 22.4 L of the stuff.What is the molar mass of a gas with a density of g/L?2.86 g/L?
50 Summary These four items are all equal: a) 1 mole b) molar mass (in grams)c) 6.02 x 1023 representative particlesd) 22.4 L at STPThus, we can make conversion factors from them.
51 Section 10.3 Percent Composition and Chemical Formulas OBJECTIVES:Calculate the percent composition of a substance from its chemical formula or experimental data.
52 Section 10.3 Percent Composition and Chemical Formulas OBJECTIVES:Derive the empirical formula and the molecular formula of a compound from experimental data.
53 Calculating Percent Composition of a Compound Like all percent problems:Part X 100%wholeFind the mass of each component,Then divide by the total mass.
54 1. Calculate the total mass. ExampleCalculate the percent composition of a compound that is g of Ag with 4.30 g of S.1. Calculate the total mass.Ag + S = 29.00g g = 33.30g
55 2. Calculate % of each element. Example2. Calculate % of each element.29.00g33.3gX 100% = 87%Ag4.30g33.3gX 100% = 13%S
56 Getting it from the formula If we know the formula, assume you have 1 mole.Then you know the mass of the pieces and the whole.Find the Molar Mass.
57 Calculate the percent composition of C2H4. ExamplesCalculate the percent composition of C2H4.C: 2 x 12.0 = 24.0gH: 4 x = g+Total Mass = 28.0g
58 2. Calculate % of each element. Example2. Calculate % of each element.24.0g28.0gX 100% = 86%C4.0g28.0gX 100% = 14%H
59 C: 0.85g X .75 =0.64g O: 0.85g X .25 =0.21g Examples If a substance which has a mass of 0.85g is 75% C and 25% 0, how much of each substance is there?C: 0.85g X .75 =0.64gO: 0.85g X .25 =0.21g
60 Show all work in Notebook!!!! HomeworkWorksheet 10-31-9Show all work in Notebook!!!!Due: 2/01/06Quiz: 2/2/06
61 The Empirical FormulaThe lowest whole number ratio of elements in a compound.The molecular formula = the actual ratio of elements in a compound.The two can be the same.
62 CH2 is an empirical formula C2H4 is a molecular formula The Empirical FormulaCH2 is an empirical formulaC2H4 is a molecular formulaC3H6 is a molecular formulaH2O is both empirical & molecular
63 Calculating Empirical Just find the lowest whole number ratioC6H12O6CH4N- CH2O- CH4N
64 Calculating Empirical It is not just the ratio of atoms, it is also the ratio of moles of atoms.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.
65 Calculating Empirical We can get a ratio from the percent composition.Assume you have a 100 g.The percentages become grams.Convert grams to moles.Find lowest whole number ratio by dividing by the smallest.
66 Calculate the empirical formula of a compound composed of 38 Calculate the empirical formula of a compound composed of % C, % H, and %N.Assume 100 g so:C: 38.67g x 1mol = 3.22 mol C12.0gH g x 1mol = mol H gN: 45.11g x 1mol = 3.22 mol N g
67 The Smallest number is 3.22mol. Divide each mole value by 3.22mol.
68 The ratio of C:N3.22 mol C = 1 mol C3.22 mol N mol NThe ratio H:N16.09 mol H = 5 mol H 3.22 mol N mol NC1H5N1
69 A compound is 43.64 % P and 56.36 % O. What is the empirical formula? Assume 100g & find moles.P:43.64g1mol30.97gX=1.41 molO:56.36g1mol16.00gX=3.52 mol
70 Ratio of P:O P2O5 Find ratio of moles. 1.41 mol of P 3.52 mol of O =P2O5Empirical Formula
71 ExampleCaffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. What is its empirical formula?Assume 100g & find moles.
72 C: H: N: O: 49.48g 1mol 12.0g X = 4.12 mol 5.15g 1mol 1.0g X =
73 Ratio of C:H:N:O Find ratio of moles. 4.12 mol of C 1.03 mol of O =5.10 mol of H1.03 mol of O5 of H1 of O=2.06 mol of N1.03 mol of O2 of N1 of O=
74 Ratio of C:H:N:O 4:5:2:1 C4H5N2O Find ratio of moles. Empirical Formula
75 Empirical to molecular Since the empirical formula is the lowest ratio, the actual molecule would weigh more.By a whole number multiple.Divide the actual molar mass by the empirical formula mass.Caffeine has a molar mass of 194 g. what is its molecular formula?
76 ExampleA compound is known to be composed of % Cl, 24.27% C and 4.07% H. Its molar mass is known (from gas density) to be g. What is its molecular formula?