Ch. 10- The Mole

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Ch. 10- The Mole

• Why- Within the next 2 months we will be working
  with chemical quantities. Determining what a
  reaction will produce or how much we need to go
  into a reaction with. These math skills can be
  applied across all science, ALL professions and
  many day to day life activities.

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Measuring Matter

• Count, Mass, Volume
• Units indicating a specific number of items
• Examples????
• Remember your dimensional analysis.well lets get
  those gears agrinding
• What is the mass of 90 apples if 1 dozen of the
  apples has a mass of 2.0kg

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Jan 25- Mole Day

• Hey you.dont be miserable todayyou dont want
  to be labeled as being dismole
• Why is it hard to count atoms, ions, or molecules
  1x1?
• We as chemists use the mole (mol) in the same way
  we use dozen
• 1 mole 6.02 x 1023 representative particles
• Avogadros number- named after him to honor his
  work on molecular theories

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• How big is a mole?
• If you count to 6.02 x 1023, one number per
  second, how long will it take?
• 6.02 x 1023 x 1min/60sec x 1hr/60min x
  1 day/24 hr x 1 yr/365 days
• 1.9 x 1016 years 19 quadrillion years!
• The earth is 4.6 billion years old, so thats 4
  million times the earths age!

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Representative particles

• Refers the the species present in a substance
• Na atoms
• CO2 molecules
• NaCl formula unit
• So
• 1 mole of Na 6.02 x 1023 atoms
• 1 mole of CO2 6.02 x 1023 molecules
• 1 mole of NaCl 6.02 x 1023 formula units

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Mole Calculations

• Representative particle mole
• The magnesium we have used in labs is used to
  make aircraft, auto wheels, tools, and garden
  furniture. How many moles of magnesium is 1.25 x
  1023 atoms of Mg
• 1.25 x 1023 atoms Mg x ______1 mole _______
• 6.02 x 1023 atoms Mg
• 2.08 x 10-1 mol Mg

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Cont.

• Moles Representative Particles
• Propane gas (C3H8) is used in cooking and
  heating. How many molecules are in 2.12 moles of
  propane.
• 2.12 mol C3H6 x 6.02 x 1023 molecules C3H6
• 1 mol C3H6

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Practice

• 1. What is Avogadros ?
• 2. What is the representative particle for MgS?
• 3. How many formula units are in 2.34 moles of
  NaNO3?
• 4. How many moles are in 3.48 x 1024 atoms of Li?

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Remember our friend amu?

• Decimal from periodic table
• Relative values based on the mass of Carbon-12
  isotope
• Since ratio is relative, changing the unit will
  not change the ratio
• Grams is convenient to use in lab so.lets us it

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Molar Mass (IMPORTANT)

• The atomic mass of an element expressed in grams
  is the mass of 1 mole of an element molar mass
• Molar mass of Mg 24.3g
• round off to 1 decimal place
• Find the Molar mass of the following
• K
• Cu
• Na
  
  How does a mole turn on
  the tv.
• .with a remolte control!!!!!

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Molar mass of Compounds

• Simplyadd the masses of all the elements in the
  compound together
• Ex. SO3
• EX. C9H11NO2
• On your owntry
• 1.) K3PO4
• 2.) Al2(SO4)3

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Mole Land. Where the fun is multiplied by 6.02 x
1023 times
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Mole Mass problems

• Use molar mass to convert between moles and mass
• When aluminum reacts with oxygen in the air a
  tough coating of aluminum oxide(Al2O3) is formed.
  What is the mass of 9.45 mol of aluminum oxide?
• molar
  mass
• 9.45 mol Al2O3 x 102.0g Al2O3 964 g
  Al2O3
• 1 mole Al2O3

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Mass Mole Problems

• How many moles of Iron (III) Oxide are contained
  in 92.2 g of pure Fe2O3?
• 92.2 g Fe2O3 x 1 mole Fe2O3 0.578 mole
  Fe2O3
• 159.6 g Fe2O3
• molar mass

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Molar Volume

• Avogadros hypothesis- equal volumes of gases at
  the same temp. and pressure contain equal number
  of particles
• Volume measured at STP (Standard Temp. and
  Pressure)
• 0C and 101.3kPa (1 atm)
• Molar volume At STP, 1 mole or 6.02 x 1023
  representative particles, of any gas occupies a
  volume of 22.4 L.

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Mole Volume Problems

• SO2 is a gas produced by the burning of coal and
  contributes to the pollution of the environment.
  Determine the volume, in L, of .60 mol SO2 at
  STP.
• .60 mol SO2 x __22.4 L 13 L SO2
• 1 mol SO2
• Molar Volume

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Volume Mole Problems

• How many moles would be contained in .200 L of H2
• .200 L H2 x 1 mole H2 8.93 x 10-3 mol H2
• 22.4 L H2
• Molar volume

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Composition

• Relative amounts of the elements in a compound
• How important in the real world
• mass of element _mass of element_ x
  100
• mass of compound

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Composition from mass data

• When a 13.60g sample of a compound containing
  only Mg and O is decomposed, 5.40g of O is
  obtained. What is the composition of this
  compound?
• O _mass of O_ x 100 5.40 g x
  100 39.7
• mass of MgO 13.60g
• Mg _mass of Mg__ x 100 8.20 g x 100
  60.3
• mass of MgO 13.60g

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Composition from Chemical Formula

• mass mass of element in 1 mol compound
• molar mass of compound
• Propane (C3H8) is commonly used in gas grills.
  What is the percent composition of Propane?
• C 36.0g x 100 81.8
• 44.0g
• H 8.0g x 100 18
• 44.0g

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Practice

• What is the percent composition for each element
  in the following compounds
• C11H12N2O2 -Tryptophan
• C6H8O6 Vitamin C
• Magnesium Phosphate

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Empirical Formula

• The lowest whole number ratio of the atoms of the
  elements in a compound
• Basic ratio (ie 121)
• May or may not be the same as the molecular
  formula
• Tells the actual of each kind of atom in the
  compound

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Determining empirical formula of a compound

• A compound is found to contain 25.9 N and 74.1
  O. What is the empirical formula of the compound
• Since means part per 100, we can assume that
  100.0g of the compound contains 25.9g and 74.1g.
• Step 1 convert to moles
• 25.9g N x 1 mol 1.85 mol N
• 14.0g
• 74.1g O x 1 mol 4.63 mol O
• 16.0g
• Step 2- Divide each molar quantity by the smaller
  molar quantity
• 1.85 mol N 1.00 mol N 4.63 mol O 2.50
  mol
• 1.85 1.85
• Step 3- Multiple each part of the ratio by the
  smallest whole that will convert both
  subscripts to whole s
• 1 mol N x 2 2 mol N
• 2.5 mol O x 2 5 mol O

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Cont

• Calculate the empirical formula for a compound
  containing 67.6 Hg, 10.8 S, and 21.6 O.
• Step 1
• 67.6g Hg x 1 mol Hg 0.337 mol Hg
• 200.6g Hg
• 10.8g S x 1 mol S 0.336 mol S
• 32.1g S
• 21.6g O x 1 mol O 1.35 mol O
• 16.0 g
• Step 2
• 0.337mol Hg 1.00mol Hg 0.336mol S 1.00mol S
  1.35mol O 4.02mol O
• 0.336 0.336 0.336