C HEMISTRY W ARM U P (B ACK TO CONVERSIONS!!!!) Convert the following: 5.5 dozen apples = _____ kg apples (1 dozen = 2.0 kg apples) 3 dozen apples = _____ bushel apples (1 dozen apples =.20 bushel apples)

S ECTION 1 T HE M OLE : A M EASUREMENT OF M ATTER What are three methods for measuring the amount of something? How is avogadro’s number related to a mole of any substance? How is the atomic mass of an element related to the molar mass of an element? How is the mass of a mole of a compound calculated? Mole Avogadro’s Number Representative Particle Molar Mass Key ConceptsVocabulary

H OW DO WE MEASURE THINGS WE CAN ’ T SEE LIKE THE ATOM ? The Mole – the animalThe Mole – chemistry

M EASURING M ATTER Measure the amount of something by: Count (how many) Mass (g) Volume (mL or cm 3 )

M ATTER Composed of: Atoms Molecules Ions Counting them would take forever!

T HE M OLE -A UNIT THAT IS A SPECIFIC NUMBER OF PARTICLES One Mole 6.02 x “representative particles” Avogadro’s Number “Representative Particles” Atoms 1 mole of Aluminum = 6.02 x atoms Molecules 1 mole of H 2 0 = 6.02 x molecules Formula Units (a.k.a. ionic compounds) 1 mole of CaF 2 = 6.02 x formula units

A MEDEO A VOGADRO DI Q UAREGNA Italian scientist Helped clarify the difference between atoms and molecules

C ONVERTING NUMBER OF R EP. PARTICLES TO MOLES Generic conversion: 1 mole = 6.02 x “representative particles” Examples: How many atoms in one mole of Copper? How many formula units in 2 moles of NaCl?

P RACTICE How many atoms are on three moles of Calcium? How many molecules are in 2.5 moles of Al 2 Cl 6 ? How many formula units are in 10 moles of NaCl?

P RACTICE W ORKSHEET

WARM UP How many moles is 2.80 x atoms of Silicon? How many formula units in 2 moles of MgBr 2 ?

C ONVERTING MOLES TO NUMBER OF ATOMS ( IN A COMPOUND ) First, figure out the number of atoms in the compound. Example: H atoms per molecule 1 mole of H 2 0 contains 6.02x10 23 molecules BUT each molecule of water contains 3 atoms Moles  Molecules  Atoms

C LASS E XAMPLE : Propane is a gas used for cooking and heating. How many atoms are in 2.12 mol of propane? (C 3 H 8 )

P RACTICE : How many atoms are in 1.14 mol of SO 3 ? How many moles are in 4.65x10 24 atoms NO 2 ?

T HE M ASS OF A M OLE OF AN E LEMENT

M OLAR M ASS Numbers under the elements on the periodic table The mass of ONE mole of a substance Example: Molar mass of Carbon = 12.0 grams 1 mole of Carbon = 12.0 grams Molar Mass of Oxygen = 16.0 grams 1 mole of Oxygen = 16.0 grams

E XAMPLE How many moles is 2 grams of Lithium? How many grams is 5 moles of Tin?

O NE M OLE OF V ARIOUS ELEMENTS

M OLAR M ASS C ONTINUED …J UST THINK! 1 mole of hydrogen has 6.02x10 23 atoms and weighs grams… 1 mole of carbon has 6.02x10 23 atoms and weighs 12 grams… How can they have the same number of atoms but weigh different amounts?

T HE M ASS OF A M OLE OF A C OMPOUND

M OLAR M ASS OF A C OMPOUND To calculate the molar mass of a compound: Separate out EACH element Count the number of that element Multiply by the molar mass Add the masses of the elements in the compound Example: SO 3 ElementNumber ofMolar Mass Total Mass S O

E XAMPLE H 2 O CH 4 C 6 H 12 O 6

S ECTION 1 A SSESSMENT - J IG SAW 1. What are three ways to measure the amount of something? 2. Describe the relationship between Avogadro’s number and one mole of any substance. 3. How is the atomic mass of an element related to the molar mass of the element? 4. How can you calculate the mass of a mole of a compound? 5. How many moles is 1.50 x molecules of NH3? 6. How many atoms are in 1.75 mol CHCl 3 ? 7. What is the molar mass of CaSO 4 ? 8. How many moles are in 4.65 x molecules of NO 2 ?

S ECTION 2 Convert the mass of a substance to the number of moles What is the volume of a gas at STP Avogadro’s hypothesis Standard Temperature and Pressure (STP) Molar Volume Key ConceptsVocabulary

T HE M OLE -M ASS R ELATIONSHIP Use the molar mass of an element or compound to convert between the mass of a substance and the mass of a substance. Conversion factor: molar mass = 1 mole Equations: Mass(grams) = number of moles x mass(grams) 1 mole Moles = number of grams x ___1 mole____ mass(grams) Molar Mass

C LASS EXAMPLES : Aluminum satellite dishes are resistant to corrosion because the aluminum reacts with oxygen in the air to form a coating of aluminum oxide (Al 2 O 3 ). This tough, resistant coating prevents any further corrosion. What is the mass of 9.45 mol of aluminum oxide?

C LASS E XAMPLE When iron is exposed to air, it corrodes to form red-brown rust. Rust is iron(iii)oxide (Fe 2 O 3 ). How many moles of iron oxide are contained in 92.2 g of pure iron oxide?

P RACTICE Find the mass in grams of 4.52 x mole C 20 H 42. Calculate the mass, in grams, of 2.50 mole of iron(ii)hydroxide.

P RACTICE Find the number of moles in 3.70 x g of boron. Calculate the number of moles in 75.0 g of dinitrogen trioxide.

P RACTICE W ORKSHEET

P RACTICE : F IND THE MASS, IN GRAMS, OF 1.00 X MOLECULES OF N 2.

P RACTICE : F IND THE MASS IN GRAMS OF 2.00 X MOLECULES OF F 2

P RACTICE : H OW MANY ATOMS OF NITROGEN ARE IN 1.2 GRAMS OF ASPARTAME ? C 14 H 18 N 2 O 5

P RACTICE : F IND THE MASS IN 2.6 X MOLECULES OF LITHIUM BROMIDE.

T HE M OLE -V OLUME R ELATIONSHIP

A VOGADRO ’ S HYPOTHESIS The equal volumes of gases at the same temperature and pressure contain equal numbers of particles Despite differences in the size of the atoms Due to the fact that the gas particles are so far apart

S.T.P. Gases are measured at Standard Temperature and Pressure B/C of variations that result in volume STP Temperature: 0 degrees Celcius (273 K) Pressure: kPa or 1 atm

M OLAR V OLUME At STP: 1 mol or 6.02 x representative particles of any gas occupies a volume of 22.4 L.

C ALCULATING VOLUME AT STP Convert MOLES of gas to the VOLUME of gas at STP Conversion factor: 22.4 L = 1 mol

C LASS E XAMPLE : Sulfur dioxide is a gas produced by burning coal. It is an air pollutant and one of the causes of acid rain. Determine the volume, in liters, of 0.60 mol sulfur dioxide at STP.

E XAMPLES What is the volume of these gases at STP? 3.20 x mol CO mol N 2

E XAMPLES At STP, how many moles does each of the following gases occupy? 1.25 L He L C 2 H 6

P RACTICE What is the volume, in Liters, of 15 g of H 2 at STP? What is the volume, in Liters, of 3.4 x molecules of O 2 at STP?

P RACTICE W ORKSHEET

C ALCULATING M OLAR M ASS FROM D ENSITY Density: Measured in grams per liter (g/L) General Equation Molar Mass = density at STP x molar volume at STP Grams = grams x 22.4L Mole L Mole

C LASS E XAMPLE The density of a gaseous compound containing carbon and oxygen is found to be g/L at STP. What is the molar mass of the compound?

E XAMPLES A gaseous compound composed of sulfur and oxygen, which is linked to the formation of acid rain, has a density of 3.58 g/L at STP. What is the molar mass of this gas?

E XAMPLES What is the density of krypton at STP?

S ECTION A SSESSMENT (10.2)