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Proportions/Rates/Fractions

Learn how to calculate molar mass, convert between grams and moles, and solve mole calculations in chemistry using proportions, rates, and fractions. Understand Avogadro's number and determine molar masses of different compounds.

lionel-duffy
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Proportions/Rates/Fractions

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  1. Proportions/Rates/Fractions • 1,500 pages in 12 days  =  ______   pages in 3 days • 18 calls in 6 hours  =  ______   calls in 11 hours

  2. Proportions/Rates/Fractions • 2,948 miles in 11 hours  =  ______   miles in 4 hours • 68 seats in 4 rows  =  ______   seats in 8 rows

  3. Molar Mass (M) • the mass (m) of one mole of a substance • mass is measured in grams (g) • molar mass is grams per mole (g/mol) • The molar masses of allelements have been determined and can be found on the Periodic Table of the Elements. • all elements are different • molar masses of all elements are different

  4. M is molar mass (in g/mol) • m is mass (in grams) • n is number of moles • Avogadro’s number = 6.022 x 1023 • To find the number of atoms/molecules you multiply the # of moles by 6.022 x 1023 • If given # of atoms/molecules you divide by avogadro’s number.

  5. Solving mole calculations • 1. Find the Molar Mass • 2. Rewrite what is given, including the units • You should always have the 3 units, moles, grams, and g/mole. • If you have atoms/molecules you need to first convert to moles by dividing by avogadro’s number. • 2. Setup equal proportions/fractions • Numerators (tops) have the same units • Denominators (bottoms) have the same units • Solve for the unknown.

  6. What is the mass of 4.7 X 10-2 mol of LiBr.

  7. Determine the number of moles of substance 8.44 g of O2

  8. What is the mass of 3.45 X 1025 atoms of Zn

  9. How many atoms, molecules, or ions would be contained in 150 g of MgSO4

  10. Molar mass • The mass of one mole is called “molar mass” • E.g. 1 mol Li = 6.94 g Li • This is expressed as 6.94 g/mol • What are the following molar masses? S SO2 Cu3(BO3)2 32.06 g/mol 64.06 g/mol 308.27 g/mol Calculate molar masses (to 2 decimal places) CaCl2 (NH4)2CO3 O2 Pb3(PO4)2 C6H12O6 110.98 g/mol (Cax1, Clx2) 96.11g/mol(Nx2, Hx8, Cx1, Ox3) 32.00 g/mol (Ox2) 811.54 g/mol (Pbx3, Px2, Ox8) 180.18 g/mol (Cx6, Hx12, Ox6)

  11. g mol g/mol Formula g/mol g mol (n) Equation HCl 0.25 g= g/mol x mol H2SO4 53.15 NaCl 3.55 Cu 1.27 Converting between grams and moles • If we are given the # of grams of a compound we can determine the # of moles, & vise-versa • In order to convert from one to the other you must first calculate molar mass g = mol x g/mol mol = g  g/mol • Thiscanberepresentedinan“equationtriangle” 36.46 9.1 98.08 0.5419 mol= g  g/mol 58.44 207 g= g/mol x mol 63.55 0.0200 mol= g  g/mol

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