mole lecture ppt

Chemical QuantitiesChemical Quantitiesoror

"Our Friend the Mole"

"Our Friend the Mole"

How you measure how How you measure how much?much?

★You can measure mass, You can measure mass, ★or volume,or volume,★or you can count pieces.or you can count pieces.★We measure mass in grams.We measure mass in grams.★We measure volume in We measure volume in

liters.liters.★We count pieces in We count pieces in MOLES.MOLES.

MolesMoles★Defined as the number of Defined as the number of

carbon atoms in exactly 12 carbon atoms in exactly 12 grams of carbon-12.grams of carbon-12.

★1 mole is 6.02 x 101 mole is 6.02 x 102323 particles.particles.

★Treat it like a very large Treat it like a very large dozendozen

★6.02 x 106.02 x 102323 is called is called Avogadro's number.Avogadro's number.

Representative particlesRepresentative particles

The smallest pieces of a The smallest pieces of a substance.substance.For an element it is an For an element it is an atomatom..Unless it is diatomicFor a molecular compound For a molecular compound it is a it is a moleculemolecule..For an ionic compound it is For an ionic compound it is a a formula unitformula unit..

Conversion factorsConversion factors

Used to change units.Used to change units.Three questionsThree questions

What unit do you want to What unit do you want to get rid of?get rid of?Where does it go to cancel Where does it go to cancel

out?out?What can you change it What can you change it

into?into?

Calculation questionCalculation question

How many molecules of COHow many molecules of CO22 are the in 4.56 are the in 4.56

moles of COmoles of CO22 ? ?

Calculation questionCalculation question

How many moles of water is 5.87 x 10How many moles of water is 5.87 x 102222 molecules?molecules?

Calculation questionCalculation question

How many atoms of carbon are there in 1.23 moles How many atoms of carbon are there in 1.23 moles of Cof C

66HH

1212OO66 ? ?

ExamplesExamples

๏ How much would 2.34 moles of carbon weigh?How much would 2.34 moles of carbon weigh?

How many moles of magnesium in 4.61 g of Mg?

How many atoms of lithium in 1.00 g of Li?

How much would 3.45 x 10How much would 3.45 x 102222 atoms of U weigh? atoms of U weigh?

ExamplesExamples

n Calculate the molar mass of the following and Calculate the molar mass of the following and tell me what type it is.tell me what type it is.

n NaNa22SS

n NN22OO44n CC

n Ca(NOCa(NO33))22

n CC66HH1212OO66

n (NH(NH44))33POPO44

Using Molar MassUsing Molar Mass

Finding moles of compoundsFinding moles of compounds

Counting pieces by weighingCounting pieces by weighing

Molar MassMolar Mass

n The number of grams in 1 mole of atoms, The number of grams in 1 mole of atoms, formula units, or molecules.formula units, or molecules.

n We can make conversion factors from these.We can make conversion factors from these.n To change grams of a compound to moles of a To change grams of a compound to moles of a

compound.compound.n Or moles to gramsOr moles to grams

For exampleFor example

How many moles is 5.69 g of How many moles is 5.69 g of NaOH?NaOH?

ExamplesExamplesHow many moles is 4.56 g of How many moles is 4.56 g of

CC88HH1818??

How many grams is 9.87 moles of How many grams is 9.87 moles of CC88HH1010NN44OO22??

How many molecules in 6.8 g of CHHow many molecules in 6.8 g of CH44??

How many atoms are there in 4.9 g of How many atoms are there in 4.9 g of NaNONaNO33??

Gases and the MoleGases and the Mole

GasesGases

They are difficult to weigh, so we’ll They are difficult to weigh, so we’ll measure volumemeasure volumeTwo things affect the volume of a gasTwo things affect the volume of a gasTemperature and pressureTemperature and pressureVolume is measured at Standard Volume is measured at Standard

Temperature and Pressure (STP) Temperature and Pressure (STP) 00oo Celcius and 1 atmosphere of Celcius and 1 atmosphere of

pressure pressure

Standard Temperature and Standard Temperature and PressurePressure

n Avogadro's HypothesisAvogadro's Hypothesis - at the same - at the same temperature and pressure equal volumes of gas temperature and pressure equal volumes of gas have the same number of particles.have the same number of particles.

n 0ºC and 1 atm pressure0ºC and 1 atm pressuren abbreviated STPabbreviated STPn At STP 1 mole of gas occupies 22.4 LAt STP 1 mole of gas occupies 22.4 Ln Called the molar volumeCalled the molar volume

ExamplesExamples

n What is the volume of 4.59 mole of COWhat is the volume of 4.59 mole of CO22 gas at gas at

STP?STP?

n How many moles is 5.67 L of OHow many moles is 5.67 L of O2 2 at STP?at STP?

n What is the volume of 8.8g of CHWhat is the volume of 8.8g of CH44 gas at STP? gas at STP?

Density of a gasDensity of a gas

n D = m /VD = m /Vn for a gas the units will be g / Lfor a gas the units will be g / Ln We can determine the density of any gas at STP We can determine the density of any gas at STP

if we know its formula.if we know its formula.n To find the density we need the mass and the To find the density we need the mass and the

volume.volume.n If you assume you have 1 mole than the mass If you assume you have 1 mole than the mass

is the molar mass (PT)is the molar mass (PT)n At STP the volume is 22.4 L.At STP the volume is 22.4 L.

ExamplesExamples

n Find the density of COFind the density of CO22 at STP.at STP.

n Find the density of CHFind the density of CH44 at STP. at STP.

The other wayThe other way

n Given the density, we can find the molar mass of Given the density, we can find the molar mass of the gas.the gas.

n Again, pretend you have a mole at STP, so V = Again, pretend you have a mole at STP, so V = 22.4 L.22.4 L.

n m = D x Vm = D x Vn m is the mass of 1 mole, since you have 22.4 L of m is the mass of 1 mole, since you have 22.4 L of

the stuff.the stuff.n What is the molar mass of a gas with a density of What is the molar mass of a gas with a density of

1.964 g/L?1.964 g/L?n 2.86 g/L?2.86 g/L?

All the things we can All the things we can changechange

Volume

IonsAtoms

Representative Particles

MassPT

Moles

6.02 x 1023

22.4 L

Count

Percent CompositionPercent Composition

n Like all percentsLike all percentsn Part x 100 %Part x 100 % whole wholen Find the mass of each component,Find the mass of each component,n divide by the total mass.divide by the total mass.

ExampleExample

n Calculate the percent composition of a Calculate the percent composition of a compound that is 29.0 g of Ag with 4.30 g of S.compound that is 29.0 g of Ag with 4.30 g of S.

Getting it from the formulaGetting it from the formula

n If we know the formula, assume you have 1 If we know the formula, assume you have 1 mole.mole.

n Then you know the pieces and the whole.Then you know the pieces and the whole.

ExamplesExamples

n Calculate the percent composition of CCalculate the percent composition of C22HH44??

n Aluminum carbonate.Aluminum carbonate.

Percent to MassPercent to Mass

n Multiply % by the total mass to find the mass Multiply % by the total mass to find the mass of that component.of that component.

n How much aluminum in 450 g of aluminum How much aluminum in 450 g of aluminum carbonate? carbonate?

Empirical FormulaEmpirical Formula

From percentage to formulaFrom percentage to formula

The Empirical FormulaThe Empirical Formula

n The lowest whole number ratio of elements in a The lowest whole number ratio of elements in a compound.compound.

n The molecular formula the actual ratio of The molecular formula the actual ratio of elements in a compound.elements in a compound.

n The two can be the same. The two can be the same. n CHCH22 empirical formula empirical formula

n CC22HH44 molecular formula molecular formula

n CC33HH66 molecular formula molecular formula

n HH22O bothO both

Finding Empirical FormulasFinding Empirical Formulas

n Just find the lowest whole number ratioJust find the lowest whole number ratio

n CC66HH1212OO66

n CHCH44NN22n It is not just the ratio of atoms, it is also the ratio It is not just the ratio of atoms, it is also the ratio

of moles of atoms.of moles of atoms.

Calculating Empirical Calculating Empirical FormulasFormulas

n Means we can get ratio from percent Means we can get ratio from percent composition.composition.

n Assume you have a 100 g.Assume you have a 100 g.n The percentages become grams.The percentages become grams.n Turn grams to moles. Turn grams to moles. n Find lowest whole number ratio by dividing Find lowest whole number ratio by dividing

everything by the smallest moles.everything by the smallest moles.

ExampleExample

n Calculate the empirical formula of a compound Calculate the empirical formula of a compound composed of 38.67 % C, 16.22 % H, and 45.11 composed of 38.67 % C, 16.22 % H, and 45.11 %N.%N.

n Assume 100 g soAssume 100 g son 38.67 g C x 1mol C = 3.220 mole C 38.67 g C x 1mol C = 3.220 mole C

12.01 gC 12.01 gC n 16.22 g H x 1mol H = 16.1 mole H 16.22 g H x 1mol H = 16.1 mole H

1.01 gH1.01 gHn 45.11 g N x 1mol N = 3.220 mole N 45.11 g N x 1mol N = 3.220 mole N

14.01 gN14.01 gN

ExampleExample

n The ratio is 3.220 mol C = 1 mol CThe ratio is 3.220 mol C = 1 mol C 3.220 molN 1 mol N 3.220 molN 1 mol N

n The ratio is 16.1 mol H = 5 mol HThe ratio is 16.1 mol H = 5 mol H 3.220 molN 1 mol N 3.220 molN 1 mol N

n CC11HH55NN11n A compound is 43.64 % P and 56.36 % O. What A compound is 43.64 % P and 56.36 % O. What

is the empirical formula?is the empirical formula?n Caffeine is 49.48% C, 5.15% H, 28.87% N and Caffeine is 49.48% C, 5.15% H, 28.87% N and

16.49% O. What is its empirical formula?16.49% O. What is its empirical formula?

Empirical to molecularEmpirical to molecular

n Caffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% Caffeine is 49.48% C, 5.15% H, 28.87% N and 16.49% O. What is its empirical formula?O. What is its empirical formula?

n Since the empirical formula is the lowest ratio the Since the empirical formula is the lowest ratio the actual molecule would weigh the same or more.actual molecule would weigh the same or more.

n By a whole number multiple.By a whole number multiple.n Divide the actual molar mass by the the mass of one Divide the actual molar mass by the the mass of one

mole of the empirical formula.mole of the empirical formula.n You will get a whole number.You will get a whole number.n Multiply the empirical formula by this.Multiply the empirical formula by this.

ExampleExample

n A compound has an empirical formula of ClCH2 and a molar mass of 98.96 g/mol. What is its molecular formula?

n A compound has an empirical formula of CH2O and a molar mass of 180.0 g/mol. What is its molecular formula?

Percent to molecularPercent to molecular

n Take the percent x the molar massTake the percent x the molar mass

– This gives you mass in one mole of the This gives you mass in one mole of the compoundcompound

n Change this to molesChange this to moles

– You will get whole numbersYou will get whole numbers

– These are the subscriptsThese are the subscriptsn Caffeine is 49.48% C, 5.15% H, 28.87% N and Caffeine 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 16.49% O. It has a molar mass of 194 g. What is its molecular formula?molecular formula?

ExampleExample

n Ibuprofen is 75.69 % C, 8.80 % H, 15.51 % O, and has a molar mass of about 207 g/mol. What is its molecular formula?