WHY? Because these are convenient ways of purchasing these items. We buy beans by the pound and eggs by the dozen.1 dozen carbon atoms = _______ carbon atoms1 dozen eggs = _____ eggs 1 dozen donuts = ______ donuts Two ways of specifying quantity: 1) Mass 2) NumberYour coworker brought in 42 donuts. How many dozen donuts did she bring to share? The counting unit used in chemistry is the MOLE (mol) 1 Mole = 6.022 x 1O23of Anything 6.022 x 1023= 602200000000000000000000 (Also called AVOGADRO'S Number)1 mole of dollar bills = 6.022 x 1023dollar bills1 mole of sand grains = _____________ sand grains1 mole of copper atoms = ___________ copper atoms Two conversion factors can be derived: 1 mole__ or 6.022 x1023objects6.022 x1023objects 1 moleHow many copper atoms are in 2.45 moles of copper?How many moles of water are equivalent to 2.97 x 1024molecules of water?Chapter 6: Chemical Composition Chapter 6 Page 1the mass in grams of 1 mole of that element or compound1 carbon-12 atom has a mass of exactly 12 amu•1 MOLE of carbon-12 atoms (6.022 x 1023carbon atoms) has a mass of exactly 12 grams•The mass standard is carbon-12. Molar Mass of an element or compound:For an element, Molar Mass is numericallyequivalent to the atomic mass What is the molar mass of Aluminum? Of bromine?Atomic number =Atomic mass = Molar mass = 11 Na22.99For a compound, Molar mass is numericallyequivalent to the formula mass molecule or formula unit)(Recall: Formula Mass= the mass of an individualMolar Mass Chapter 6 Page 2Molar mass can be used as a conversion factor:mass moles moles massHow many grams of aluminum are in 1.68 moles of Al?What is the mass (in grams) of 2.45 moles of CO2?How many moles of water are equivalent to 8.50 grams of water?How many moles of NaCl are in 152.0 g NaCl?What is the formula mass and molar mass of water?Formula Mass of Molar Mass of 1 H2O molecule 1 mole of H2O molecules H 2 x 1.008 amu = 2.016 amu 2 x 1.008 g = 2.016 g O 1 x 16.00 amu = 16.00 amu 1 x 16.00 g = 16.00 g 18.016 amu 18.016 g per molecule per mole of H2O of H2OFormula Mass of H2O = 18.02 amu Molar Mass of H2O = 18.02 g/mole 18.02 amu 18.02 gMass to Mole/Mole to Mass Conversions Chapter 6 Page 3# of particles # of molesWe have used Avogadro's number as a conversion factor to convert: # of moles # of particleswhere the particles are usually atoms, molecules or formula units (Avogadro's number) 1 mole = 6.022 x 1023particlesWe have used molar mass as a conversion factor to convert: mass (g) # of moles # of moles mass (g)We can use both Avogadro's number and molar mass to do TWO STEP conversions:MASS (g) # of MOLES # of PARTICLESHow many atoms of chromium (Cr) are in 8.65 g of Cr?Use molar mass as Conversion factorUse Avogadro's numberas Conversion factorConversions between Mass, Moles and Number of Particles Chapter 6 Page 4If there are 7.58 X 1021molecules of hexane present in a sample of hexane (molecular formula = C6H14), how many grams of hexane are there? How many molecules of nitrogen gas (N2) are in 42.8 g of nitrogen gas?1.45 x 1024atoms of Fe is equivalent to how many grams of iron? Using Chemical Formulas in ConversionsThere is ANOTHER conversion we can do:MASS (g) # of MOLES # of PARTICLESMoles of aCompoundMoles of an ElementWithin a CompoundUse mole ratiodetermined from the formula as conversion factor To determine the MOLE RATIOS from a formula, look at the subscripts of the elements that make up that compound……. Conversions between Mass, Moles and Number of Particles Chapter 6 Page 51 mole Li3PO4contains…___ moles Li___ moles P___ moles OExample:So the mole ratios are: How many moles of oxygen are in 2.65 moles of Li3PO4? How many moles of Li are in this compound? Of Phosphorus?Moles of aCompoundMoles of an ElementWithin a CompoundUse mole ratiodetermined from the formula as conversion factor How many moles of C are in 0.955 moles of glucose (C6H12O6)?Using Chemical Formulas in Conversions Chapter 6 Page 6of a CompoundMASS (g) # of MOLES # of PARTICLES # of MOLES of an MASS (g) Element Within # of PARTICLES a CompoundPutting it ALL together to solve more complex problems:How many sodium cations are in 1.50 moles of Na2SO4?UseAvogadro's numberas conversion factorUse Molar massas conversion factorUse mole ratioas conversion factorHow many moles of hydrogen are in 1.68 g of H2O? How many hydrogen atoms are in this mass of water?How many molecules of sulfur dioxide (SO2) are present in 5.88 g of SO2? How many atoms of oxygen are in this mass of SO2? 3.70 g Fe2(CO3)3contains how many grams of Fe?More Complex Conversions Chapter 6 Page 7Mass Percent Composition= Percentage (by mass) of each element in a compoundWhat is the mass percent of calcium in CaBr2?1st step: Determine the molar mass of the compound:2nd step: Determine the molar mass of Ca in the compound.Mass % = x 100% Mass of element in 1 mol cmpd Mass of 1 mol compound 3rd step: Determine the mass percent of Ca in the compound.What is the mass percent of bromine in CaBr2?Determine the percent composition of each element in H2SO4.Mass Percent Composition Chapter 6 Page 8Silver chloride (AgCl) contains 75.27% by mass of silver (Ag). What is the % by mass of Cl?Use mass percent to determine a conversion factor If a sample contains 4.95 grams of silver chloride, how many grams of Ag are present in the sample? % Ag = 75.27% % Cl = 24.73 % In 100 g of AgCl there are:______ g of Cl ______ g of Ag in AgClSo, the conversion factors are: How many grams of Ag are present in 4.95 grams of silver chloride? How many grams of chlorine are present in this sample?Using Mass Percent as a Conversion Factor Chapter 6 Page