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Molar Mass (M) Topic 1.2 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 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 CO2 is 44 g/mol 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 Calculate the Molar Mass of Na3PO4. Atom Na P O # 3 1 4 Atomic Mass X 23.0 X 31.0 X 16.0 Total = = = = Total 69.0 31.0 64.0 164.0 Therefore the molar mass is 164.0 g mol-1 • 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 Converting Moles to Grams and Grams to Moles conversion factor will be: 1 mole molar mass OR molar mass__ 1 mole Number of moles to mass(g) • Find the mass (in grams) of 1.93 moles of MgO? 1.93 mol MgO 1 x 40.3 g MgO 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 1 x 1 mole MgO 40.3 g MgO = 0.583 mol MgO Number of grams to moles to particles • Find the number of particles in 13.9 g of MgO? 13.9 g MgO x 1 1 mole MgO_ x _6.02 X 1023 particles MgO 40.3 g MgO 1 mole MgO = 2.07 X 1023 particles of MgO here it is again combining two conversion factors 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) same thing but be careful if you do this! What is the mass of 2.55 × 1023 atoms of lead? 2.55 × 1023 atoms Pb × 1 mol Pb 207.2 g Pb × 23 1 mole Pb 6.02×10 atoms Pb = 87.8 g Pb How many atoms in 22 grams of copper? The Mole Road Map Mass “Stuff” 6.022 x 1023 mole mole g Stuff: g mole Mole mole . 6.022 x 1023 mole . 22.7 L 22.7 L mole •Atoms •Molecules •Particles •Electrons •Ions •Formula Units For Gases only: @ STP (Standard Temp & Pressure) (0 oC (273 K) & 1 atm) Volume