Chemical Quantities Chemical Quantities (the MOLE)(the MOLE)Chapter 10Chapter 10

Counting UnitsCounting Units

How many is a dozen? How many is a dozen? How many does the word “couple” stand How many does the word “couple” stand

for?for? How many sheets are in a ream of paper?How many sheets are in a ream of paper?

Answers: 12, 2, 500Answers: 12, 2, 500

Chemist’s “Dozen”Chemist’s “Dozen”

Chemists also have a counting unit for a Chemists also have a counting unit for a certain number of thingscertain number of things

A A mole mole = Avogadro’s number of things= Avogadro’s number of things 1 mole = 6.02 x 101 mole = 6.02 x 102323 things things

– Could be atoms, ions, particles, molecules, etc.Could be atoms, ions, particles, molecules, etc.

How big is that number? How big is that number? – See Sheet: A mole is a lot of thingsSee Sheet: A mole is a lot of things

Sample ProblemSample Problem

How many atoms are contained in 4.5 moles How many atoms are contained in 4.5 moles of copper?of copper?

How many moles are in 8.3 x 10How many moles are in 8.3 x 102424 molecules molecules of water? of water?

Answers: 2.71 x 10 24 atoms, 13.8 molesAnswers: 2.71 x 10 24 atoms, 13.8 moles

Masses and MolesMasses and Moles

If you had a dozen bowling balls and a If you had a dozen bowling balls and a dozen ping pong balls, which would have dozen ping pong balls, which would have more mass? Why?more mass? Why?

The bowling balls would have more mass The bowling balls would have more mass because each individual bowling ball has because each individual bowling ball has more mass than a ping pong ball.more mass than a ping pong ball.

Mass of Elements and MolesMass of Elements and Moles

Which would be heavier: a mole of copper Which would be heavier: a mole of copper or a mole of lead? Why?or a mole of lead? Why?

A mole of lead would be heavier because an A mole of lead would be heavier because an atom of lead is heavier than an atom of atom of lead is heavier than an atom of copper (64 amu vs. 207 amu)copper (64 amu vs. 207 amu)

Carbon-12 and Avogadro’s NumberCarbon-12 and Avogadro’s Number

Avogadro’s number is related to the mass of Avogadro’s number is related to the mass of an element, specifically carbon (the isotope an element, specifically carbon (the isotope carbon-12)carbon-12)

Used exactly 12 grams of carbon and Used exactly 12 grams of carbon and determined the number of atoms in that determined the number of atoms in that sample sample

There are 6.02 x 10There are 6.02 x 102323 atoms in 12 grams of atoms in 12 grams of carbon (1 mole)carbon (1 mole)

Definition of MoleDefinition of Mole

A moleA mole is the amount is the amount of matter that contains of matter that contains as many objects as many objects (atoms, molecules, (atoms, molecules, etc.) as the number of etc.) as the number of atoms in exactly 12 g atoms in exactly 12 g of of 1212C. C. – Mole connects amu & Mole connects amu &

gram = “Chemists gram = “Chemists dozen”dozen”

Molar MassMolar Mass

How do you determine moles if you have a How do you determine moles if you have a compound?compound?

What is the mass of 1 mole of NaCl?What is the mass of 1 mole of NaCl? Answer: 58 g/molAnswer: 58 g/mol Molar Mass: Molar Mass: the mass of one mole of a the mass of one mole of a

substance (element or compound)substance (element or compound)

Sample Problem- molar massSample Problem- molar mass

What is the mass of one mole of What is the mass of one mole of – water?water?– Carbon dioxide?Carbon dioxide?

– CC66HH1212OO66 (glucose) (glucose)

– Ca(NOCa(NO33))22

– Answers: 18 g/ mol, 44, 180, 164Answers: 18 g/ mol, 44, 180, 164

Sample Problem- moles to massSample Problem- moles to mass

How many grams of sodium chloride (NaCl) How many grams of sodium chloride (NaCl) did you use if you put 0.250 moles of it on did you use if you put 0.250 moles of it on your French fries?your French fries?

Answer: 14.5 gAnswer: 14.5 g

Sample Problem – mass to molesSample Problem – mass to moles

How many moles of helium are in a balloon How many moles of helium are in a balloon that contains 4.5 g of helium?that contains 4.5 g of helium?

Answer: 1.1 molesAnswer: 1.1 moles

Molar VolumeMolar Volume

Can you determine moles from the volume Can you determine moles from the volume of a substance?of a substance?– For solids and liquids: must use densityFor solids and liquids: must use density– For gases: related to the temperature and For gases: related to the temperature and

pressure of the gas.pressure of the gas.

Avogadro’s HypothesisAvogadro’s Hypothesis

Equal volumes of gases at the same Equal volumes of gases at the same temperature and pressure contain the same temperature and pressure contain the same number of moleculesnumber of molecules

All gases behave the same way, no matter All gases behave the same way, no matter the chemical identitythe chemical identity

Standard Temp and PressureStandard Temp and Pressure

Because the volume of a gas depends on Because the volume of a gas depends on the temp and pressure of the gas, a the temp and pressure of the gas, a standard reference is necessarystandard reference is necessary

STP: Standard Temperature and PressureSTP: Standard Temperature and Pressure– Std Temp: 0Std Temp: 0ooC or 273 KC or 273 K– Std Press: 101.3 kPa or 1 atmStd Press: 101.3 kPa or 1 atm

1 mole of a gas at STP = 22.4 L 1 mole of a gas at STP = 22.4 L

Sample Problem – Volume to molesSample Problem – Volume to moles

How many moles of helium are in a balloon How many moles of helium are in a balloon has a volume of 6.40 L? (at STP)has a volume of 6.40 L? (at STP)

Answer: .286 molesAnswer: .286 moles

Study Buddy ReviewStudy Buddy Review

What is Avogadro’s Number?What is Avogadro’s Number? What is a mole?What is a mole? What is molar mass?What is molar mass? How do you find the molar mass of a How do you find the molar mass of a

compound?compound? What is STP?What is STP?

Percent CompositionPercent Composition

Penny CompositionPenny Composition

Remember: a penny’s composition has Remember: a penny’s composition has changed through the yearschanged through the years– Most recent change 1982Most recent change 1982

If a post-1982 penny is 2.500 g and it has If a post-1982 penny is 2.500 g and it has 0.0625 g copper, what percentage is 0.0625 g copper, what percentage is copper? What percentage is zinc?copper? What percentage is zinc?

Answers: 2.50 % Cu, 97.50 % ZnAnswers: 2.50 % Cu, 97.50 % Zn

Percent CompositionPercent Composition

mass of each mass of each element in element in compound compound compared to compared to the entire the entire mass of the mass of the compound, compound, multiplied by multiplied by 100%100%

Sample ProblemSample Problem

What is the percentage composition of What is the percentage composition of copper in chalcocite, Cucopper in chalcocite, Cu22S?S?

Answer: 80 %Answer: 80 %

Consider theseConsider these

CC66HH1212OO66 glucose (blood), fructose (corn glucose (blood), fructose (corn

syrup)syrup)

CC55HH1010OO55 ribose (RNA), xyloseribose (RNA), xylose

What do the formulas have in common?What do the formulas have in common?

Empirical formulasEmpirical formulas

CHCH22OO smallest whole number ratiosmallest whole number ratio

Carbohydrates: CCarbohydrates: Cnn(H(H22O)O)nn

Empirical Formulas:Empirical Formulas: smallest whole number smallest whole number ratio of the atoms in a substanceratio of the atoms in a substance

Molecular FormulasMolecular Formulas

Molecular Formula:Molecular Formula: whole number multiple whole number multiple of empirical – of empirical – – tells the actual number of atoms in a substance tells the actual number of atoms in a substance

as it exists in natureas it exists in nature– Can be the same as the empirical formulaCan be the same as the empirical formula