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Ch. 10- The Mole

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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Ch. 10- The Mole

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  1. 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.

  2. 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

  3. Jan 25- “Mole Day” • Hey you….don’t be miserable today…you don’t 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 • Avogadro’s number- named after him to honor his work on molecular theories

  4. 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 that’s 4 million times the earth’s age!

  5. 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 1023atoms • 1 mole of CO2 = 6.02 x 1023molecules • 1 mole of NaCl = 6.02 x 1023formula units

  6. 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 1023atoms Mg x ______1 mole _______ = 6.02 x 1023atoms Mg 2.08 x 10-1 mol Mg

  7. 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

  8. Practice • 1. What is Avogadro’s #? • 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?

  9. 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

  10. 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!!!!!”

  11. Molar mass of Compounds • Simply…add the masses of all the elements in the compound together • Ex. SO3 • EX. C9H11NO2 On your own…try 1.) K3PO4 2.) Al2(SO4)3

  12. Mole Land…. Where the fun is multiplied by 6.02 x 1023 times

  13. 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 molAl2O3 x 102.0g Al2O3 = 964 g Al2O3 1 mole Al2O3

  14. 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

  15. Molar Volume • Avogadro’s hypothesis- equal volumes of gases at the same temp. and pressure contain equal number of particles • Volume measured at STP (Standard Temp. and Pressure) • 0°C 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.

  16. 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 molSO2 x __22.4 L = 13 L SO2 1 molSO2 Molar Volume

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

  18. % 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

  19. % 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% = 5.40g x 100% = 39.7% mass of MgO 13.60g % Mg= _mass of Mg__ x 100% = 8.20g x 100% = 60.3% mass of MgO 13.60g

  20. % 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

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

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