2Chemical Quantities or Chapter 10Chemical Quantitiesor"Our Friend the Mole"
3How you measure how much? 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.
4Moles 1 mole is 6.02 x 1023 particles. Particles can be atoms, molecules, formula units.6.02 x is called Avogadro's number.
5Representative particles The smallest pieces of a substance.For an element it is an atom.Unless it is diatomicFor a molecular compound it is a molecule.For an ionic compound it is a formula unit.
6Conversion factors Used to change units. Three questions What unit do you want to get rid of?Where does it go to cancel out?What can you change it into?
7Calculation questionHow many molecules of CO2 are the in 4.56 moles of CO2 ?4.56 moles CO2 x 6.02 x 1023 Molecules = 2.75 x 1024 Molecules CO21 Mole CO2
8Calculation question How many moles of water is 5.87 x 1022 molecules? 5.87 x 1022 molecules H2O x 1 Mole H2O____________ = Moles H2O6.02 x 1023 Molecules H2O
9Calculation questionHow many atoms of carbon are there in 1.23 moles of C6H12O6 ?1.23 moles C6H12O6 x 6 moles C Atoms_____ x 6.02 x 1023 Atoms C1 mole C6H12O6 Molecules mole C atoms= 4.44 x atoms C
10Measuring Moles The decimal number on the periodic table is The mass of the average atom in amuThe mass of 1 mole of those atoms in grams.
11Gram Atomic MassGram Atomic Mass is the mass of 1 mole of an element in grams.We can write this as g C = 1 moleWe can count things by weighing them.
12Examples How much would 2.34 moles of carbon weigh? 2.34 moles C x 12 g C__ = 28.1 g C1 mole C
13Examples How many moles of magnesium in 4.61 g of Mg? 4.61 g Mg x 1 mole Mg = moles Mg24.3 g Mg
14Examples How many atoms of lithium in 1.00 g of Li? 1.00 g Li x 1 mole Li x x 1023 atoms Li = 8.7 x atoms Li6.9 g Li mole Li
15Examples How much would 3.45 x 1022 atoms of U weigh? 3.45 x 1022 atoms U x 1 mole U_________ x 238g U = g U6.02 x 1023 atoms U mole U
16What about compounds?In 1 mole of H2O molecules there are two moles of H atoms and 1 mole of O atoms. (Be careful)To find the mass of one mole of a compoundDetermine the moles of the elements contained in the compound.Find out how much each would weighadd them up
17What about compounds?Molar Mass is the mass of one mole of any compound. Example: What is the Molar mass of CH4?1 mole of C = g4 mole of H = 4 x 1.01 g = 4.04g1 mole CH4 = = 16.05g/mol
18Molar Mass What is the molar mass of Fe2O3? 2 moles of Fe = 2 x g = g3 moles of O = 3 x g = gThe Molar mass = g g = g/mol
19Calculate the molar mass of the following C6H12O6C = 6 x 12g = 72gH = 12 x 1.0g = 12gO = 6 x 16g = 96gMolar mass = = 180g/mol(NH4)3PO4N = 3 x 14g = 42gP = 1 x 30.9g = 30.9gO = 4 x 16g = 64gMolar mass = 42g + 12g g + 64g = 148.9g/mol
20Finding moles of compounds Counting pieces by weighing Using Molar MassFinding moles of compoundsCounting pieces by weighing
21Molar MassThe number of grams in 1 mole of atoms, formula units, or molecules.We can make conversion factors from these.To change grams of a compound to moles of a compound.Or moles to grams
22For example How many moles is 5.69 g of NaOH? 5.69 g NaOH x 1 mole NaOHMolar mass of NaOHMolar Mass NaOH = Na + O + H = 23.0g+16g + 1.0g = 40g/moleSubstitute 40g/mole into the equation above and get:5.69 g NaOH x 1 mole NaOH = 0.14 moles NaOH40 g NaOH
24Gases Many of the chemicals we deal with are gases. They are difficult to weigh, so we’ll measure volumeNeed to know how many moles of gas we have.Two things affect the volume of a gasTemperature and pressureCompare at the same temp. and pressure.
25Standard Temperature and Pressure Avogadro's Hypothesis - at the same temperature and pressure equal volumes of gas have the same number of particles.0ºC and 1 atmosphere pressureAbbreviated atm273 K and kPakPa is kiloPascal
26At Standard Temperature and Pressure abbreviated STPAt STP 1 mole of gas occupies 22.4 LCalled the molar volumeUsed for conversion factorsMoles to Liter (x 22.4), and L to mol (divide by 22.4)
27Examples What is the volume of 4.59 mole of CO2 gas at STP? 4.59 mole CO2 x 22.4L CO = L CO21 mole CO2
28Density of a gas D = m /V for a gas the units will be g / L We 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 than the mass is the molar mass (PT)At STP the volume is 22.4 L.
29ExamplesFind the density of CO2 at STP. Note: At STP the volume is 22.4 LD =m/v = Molar mass CO2 = ((12g + (16g x 2g)) = 1.96g/l22.4 L L
30Quizdom Find the density of CH4 at STP. D=m/v ((12.0g +(1.0g x 4)) = g/l22.4L
31The other wayGiven the density, we can find the molar mass of the gas.Again, pretend you have a 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? M=D x V = 1.964g/l x 22.4L = 44g
33Mass Volume Moles 6.02 x 1023 Representative Particles Ions Atoms PTMolesRepresentativeParticles6.02 x 1023IonsAtomsCount
34Percent Composition Like all percents Part x 100 % whole Find the mass of each component,divide by the total mass.
35ExampleCalculate the percent composition of a compound that is 29.0 g of Ag with 4.30 g of S.Part x 100WholeTotal weight = 29.0g Ag g S = 33.3 g%Ag = 29.0g Ag x 100 = 87.1% Ag33.3 g% S = 4.30g S x 100 = 12.9% S33.3g
36Getting it from the formula If we know the formula, assume you have 1 mole.Then you know the pieces and the whole.
37Examples Calculate the percent composition of C2H4? Assume 1 mole 1 mole C2H4 = (12g x 2) +(1.0g x 4) = 28g/mole total mass% C = (12g x 2) x = 85.7% C28 g% H = (1.0g x 4) x = 14.3% H
38Examples What is the percent composition of Aluminum carbonate. Write the formula: Al2(CO)3 (ionic Formula writing)Assume 1 moleCalculate Total Mass: (Al x 2) + (C x 3) + (O x 3) = (27g x 2) + (12g x 3) + (16g x 3) = 54g + 36g + 48g = 138g% Al = (27g x 2) x = 39.1%Al138g% C = (12g x 3) x = 26.1% C% O = (16g x 3) x = % O
39Percent to MassMultiply % by the total mass to find the mass of that component.How much aluminum in 450 g of aluminum carbonate?Write the formula: Al2(CO)3 (ionic Formula writing)% Al = (27g x 2) x = 39.1%Al138g% C = (12g x 3) x = 26.1% C% O = (16g x 3) x = % O39.1%Al x1/100 x 450g Al2(CO)3 = 176g Al
40From percentage to formula Empirical FormulaFrom percentage to formula
41The 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.CH2 empirical formulaC2H4 molecular formulaC3H6 molecular formulaH2O both
42Finding Empirical Formulas Just find the lowest whole number ratioC6H12O6CH4N2It is not just the ratio of atoms, it is also the ratio of moles of atoms.
43Calculating Empirical Formulas Means we can get ratio from percent composition.Assume you have a 100 g.The percentages become grams.Turn grams to moles.Find lowest whole number ratio by dividing everything by the smallest moles.
44ExampleCalculate the empirical formula of a compound composed of % C, % H, and %N.Assume 100 g so38.67 g C x 1mol C = mole C gC16.22 g H x 1mol H = 16.1 mole H gH45.11 g N x 1mol N = mole N gN
45Example The ratio is 3.220 mol C = 1 mol C 3.220 molN 1 mol N The ratio is mol H = 5 mol H molN mol NC1H5N1Caffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. What is its empirical formula?
46Empirical to molecular Caffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. What is its empirical formula?Since the empirical formula is the lowest ratio the actual molecule would weigh the same or more.By a whole number multiple.Divide the actual molar mass by the the mass of one mole of the empirical formula.You will get a whole number.Multiply the empirical formula by this.
47ExampleA compound has an empirical formula of ClCH2 and a molar mass of g/mol. What is its molecular formula?A compound has an empirical formula of CH2O and a molar mass of g/mol. What is its molecular formula?
48Percent to molecular Take the percent x the molar mass This gives you mass in one mole of the compoundChange this to molesYou will get whole numbersThese are the subscriptsCaffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. It has a molar mass of 194 g. What is its molecular formula?
49ExampleIbuprofen is % C, 8.80 % H, % O, and has a molar mass of about g/mol. What is its molecular formula?