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Molar Mass (M) Topic 1.2

Molar Mass (M) Topic 1.2. Mass. relative atomic mass ( A r ) all masses on the periodic table are compared to CARBON- 12 no units are necessary since it is just a comparison to carbon- 12 from this we get the average atomic mass that you would find for an element on the periodic table.

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Molar Mass (M) Topic 1.2

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  1. Molar Mass (M) Topic 1.2

  2. Mass • relative atomic mass (Ar) • all masses on the periodic table are compared to CARBON- 12 • no units are necessary since it is just a comparison to carbon- 12 • from this we get the average atomic mass that you would find for an element on the periodic table

  3. relative molecular mass (Mr) • simply comparing a given molecule to carbon • CO2 is 44. C60 is 720, O2 is 16(2) = 32 • atomic or molecular mass • this is simply the mass of one atom or molecule using a very small unit of measurement called a.m.u. • therefore CO2 is 44 a.m.u. • molar mass (M) • this is how many grams you would have in a mole of a substance • therefore CO2is 44 g/mol

  4. molar mass continued… • simply change the relative atomic mass from the periodic table for the element/molecule/ compound to grams • oxygen’s atomic mass is 16.00 amu • therefore 1 mole of oxygen has a molar mass is 16.00 g/mol • sugar’s (C6H12O6) atomic mass is 180.0 amu • carbon: 12.00(6) = 72.00 • hydrogen: 1.00(12) = 12.00 • oxygen: 16.00(6) = 96.00 • therefore 1 mole of sugar has a molar mass of 180.00 g/mol

  5. Calculate the Molar Mass of Na3PO4. Therefore the molar mass is 164.0 g mol-1

  6. Give the molar mass (mass of one mole): • Fe → 55.9 g/mol • C2H6 → 30.1 g/mol • Fe(OH)2 → 89.9 g/mol • C12H22O11 → 342.3 g/mol • CuSO4 · 5 H2O → 238 g/mol

  7. Converting Moles to Grams and Grams to Moles • conversion factor will be: • 1 mole molar mass OR • molar mass__ 1 mole

  8. Number of moles to mass(g) • Find the mass (in grams) of 1.93 moles of MgO? 1.93 mol MgO x 40.3 g MgO 1 1 mol MgO = 77.8 g MgO Mass(g) to moles • Find the number of moles in 23.5 g of MgO? • 23.5 g MgO x 1 mole MgO • 1 40.3 g MgO = 0.583 mol MgO

  9. Number of grams to moles to particles • Find the number of particles in 13.9 g of MgO? • 13.9 g MgO x 1 mole MgO_ x _6.02 X 1023 particles MgO • 1 40.3 g MgO 1 mole MgO • 1 mole MgO_ x _6.02 X 1023 particles MgO • 40.3 g MgO 1 mole MgO • 6.02 X 1023 particles MgO • 40.3 g MgO molar mass (g) = 2.07 X 1023 particles of MgO here it is again combining two conversion factors same thing but be careful if you do this!

  10. 1 mol Pb 207.2 g Pb 2.55 × 1023 atoms Pb × × 1 mole Pb 6.02×1023 atoms Pb • What is the mass of 2.55 × 1023 atoms of lead? = 87.8 g Pb

  11. How many atoms in 22 grams of copper?

  12. The Mole Road Map “Stuff” Mass 6.022 x 1023 mole mole g • Stuff: • Atoms • Molecules • Particles • Electrons • Ions • Formula Units Mole g mole mole . 6.022 x 1023 22.7 L mole mole . 22.7 L For Gases only: @ STP (Standard Temp & Pressure) (0 oC (273 K) & 1 atm) Volume

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