QRT Sept 24

# QRT Sept 24 - Section R02 3 70 75 78 80 70 How many...

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September 25, 2007 Section R02 3: 70, 75, 78, 80 70. How many molecules of this CFC are you releasing to the air when you empty the can? 250 grams CCl 2 F 2    X                        1 mole CCl     2 F                  = 2.0676 mol               120.9135 grams CCl 2 F 2 2.0676 mol  X  6.022 x 10     23     molecules      =    1.25 x 10 24  molecules 1 mol 75. Calculate the molar mass of each of these compounds and the mass percent of each  element. a. PbS, lead (II) sulfide, galena 201.2(1)+ 32.065(1)= 233.265 g/mol % Pb=    Mass of Pb in 1 mol PbS       x 100% = 201.2 grams Pb   x 100% =  86.3% Pb Mass of PbS in 1 mol of PbS             233.265 g PbS % S =     Mass of S in 1 mol PbS       x 100% =   32.065 grams S   x 100% =  13.8% S Mass of PbS in 1 mol of PbS             233.265 g PbS b. C 2 H 6 , ethane, a hydrocarbon fuel 12.0107(2)+ 1.0079(6)= 30.0688 g/mol

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