4.3  APPLICATION EXAMPLE FOR MOLES  Gas Behavior How does the behavior of gases affect airbags?

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• 4.3 APPLICATION EXAMPLE FOR MOLES Gas BehaviorHow does the behavior of gases affect airbags?

• What is pressure?Pressure Force of gas particles running into a surface

• As number of molecules increases, there are more molecules to collide with the wallCollisions between molecules and the wall increasePressure increasesIf pressure is molecular collisions with the containerAs # of molecules increases, pressure increasesPressure and Number of Molecules

• Pressure and VolumeAs volume increases, molecules can travel farther before hitting the wallCollisions between molecules and the wall decreasePressure decreasesIf pressure is molecular collisions with the containerAs volume increases, pressure decreases

• Section 4.3Counting MoleculesSo the number of molecules affects pressure of an airbaghow do we count molecules?

• How do auto makers utilize enough atoms of gas to create pressure that inflates the bag,

But not so many that the pressure is too great when it hits you and your face that it causes permanent damage

Count the atoms

• What is a mole?

• DefinitionMole SI unit for countingThe only acceptable abbreviation for mole is molnot m!!

• What is a counting unit?Youre already familiar with one counting unita dozenDozen12A dozen doughnuts 12 doughnutsA dozen booksA dozen carsA dozen people 12 books 12 cars 12 peopleA dozen = 12

• What does a mole count in?A mole = 6.02 1023 (called Avogadros number)mole6.02 10231 mole of doughnuts 6.02 1023 doughnuts1 mole of atoms1 mole of molecules 6.02 1023 atoms 6.02 1023 molecules6.02 1023 = 602,000,000,000,000,000,000,000This means a 12 ounce bottle of water would have 19.7 moles of watera much easier-to-work-with number!

• Molar Mass

• DefinitionMolar Mass The mass for one mole of an atom or molecule.Other terms commonly used for the same meaning:Molecular WeightMolecular MassFormula WeightFormula Mass

• Mass for 1 mole of atomsThe average atomic mass = grams for 1 moleElementMass1 mole of carbon atoms 12.01 g1 mole of oxygen atoms1 mole of hydrogen atoms 16.00 g 1.01 gUnit for molar mass: g/mole or g/molAverage atomic mass is found on the periodic table

• Molar mass for moleculesThe molar mass for a molecule = the sum of the molar masses of all the atoms

• Calculating a Molecules MassCount the number of each type of atomFind the molar mass of each atom on the periodic tableMultiple the # of atoms molar mass for each atomFind the sum of all the masses1234To find the molar mass of a molecule:

• Example: Molar MassExample:Find the molar mass for CaBr2

• Example: Molar MassCount the number of each type of atom1CaBr12Example:Find the molar mass for CaBr2

• Example: Molar MassFind the molar mass of each atom on the periodic table2CaBr1240.08 g/mole79.91 g/moleExample:Find the molar mass for CaBr2

• Example: Molar MassMultiple the # of atoms molar mass for each atom3CaBr1240.08 g/mole79.91 g/moleExample:Find the molar mass for CaBr2=40.08 g/mole=159.82 g/mole

• Example: Molar MassFind the sum of all the masses4CaBr1240.08 g/mole79.91 g/mole=40.08 g/mole=159.82 g/mole+199.90 g/mole1 mole of CaBr2 molecules would have a mass of 199.90 gExample:Find the molar mass for CaBr2

• Example: Molar Mass & ParenthesisBe sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.Example:Find the molar mass for Sr(NO3)2

• Example: Molar Mass & ParenthesisBe sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.1687.62 g/mole16.00 g/mole=87.62 g/mole=96.00 g/mole+211.64 g/mole1 mole of Sr(NO3)2 molecules would have a mass of 211.64 g214.01 g/mole=28.02 g/moleSrNOExample:Find the molar mass for Sr(NO3)2

• Lets Practice #2Example:Find the molar mass for Al(OH)3

• Lets Practice #2Be sure to distribute the subscript outside the parenthesis to each element inside the parenthesis.1326.98 g/mole1.01 g/mole=26.98 g/mole=3.03 g/mole+78.01 g/mole1 mole of Al(OH)3 molecules would have a mass of 78.01 g316.00 g/mole=48.00 g/moleAlOHExample:Find the molar mass for Al(OH)3

• Using Molar Mass in Conversions

• Example: Moles to GramsExample:How many grams are in 1.25 moles of water?

• Example: Moles to Grams1.25 mol H2O= _______ g H2Omol H2Og H2O18.02122.53When converting between grams and moles, the molar mass is needed1 mole H2O molecules = 18.02 gExample:How many grams are in 1.25 moles of water?

• Lets Practice #3Example:How many moles are in 25.5 g NaCl?

• Lets Practice #325.5 g NaCl= _______ mole NaClg NaClmole NaCl158.440.441 mole NaCl molecules = 58.44 gExample:How many moles are in 25.5 g NaCl?

• Lets Practice #4Example:How many grams is a sample of 2.75 1024 molecules of SrCl2?

• 2.75 1024 molecules SrCl2Lets Practice #4= _________ g SrCl2molecules SrCl2mol SrCl216.02 10237.241 mol = 6.021023 molecules1 moles SrCl2 molecules = 158.52 gmol SrCl2g SrCl2158.521Example:How many grams is a sample of 2.75 1024 molecules of SrCl2?

• Example: Grams to MoleculesExample:How many molecules are in 25.5 g NaCl?

• 25.5 g NaClExample: Grams to Molecules= _________ molecules NaClg NaClmol NaCl158.442.63 10231 mol = 6.021023 molecules1 moles NaCl molecules = 58.44 gmol NaClmolecules NaCl6.0210231Example:How many molecules are in 25.5 g NaCl?

********What is molar mass?**************What is molar mass?********