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Understanding Avogadro's Number and Molar Mass in Chemistry

Learn about the mole concept, Avogadro's number, molar mass calculations, and converting moles to grams or particles in chemistry. Get familiar with essential concepts for chemistry calculations.

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Understanding Avogadro's Number and Molar Mass in Chemistry

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  1. Avogadro, The Mole, and Grams HAHS

  2. The Mole • The amount of substance that contains as many particles as there are atoms in exactly 12 g of carbon. • We can think of the mole is a counting unit for chemists. • Examples: • 1 dozen =12 • 1 ream of paper = 500 sheets

  3. Avogadro’s Number • Is the number of particles in exactly one mole of a pure substance. • 6.02 x 1023 is called “Avogadro’s Number” in honor of the Italian chemist Amadeo Avogadro (1776-1855). I didn’t discover it. Its just named after me!

  4. Avogadro’s Number (con’t) • There is 602000000000000000000000 atoms in 1 mole of a substance THAT’S A GIGANTIC NUMBER!!!!!!!!!

  5. Molar Mass • Is the mass of 1 mole of a per substance • Has units of grams per mole (g/mol) • Equaled to the atomic mass of the element or compound.

  6. Molar Mass of a Compound • Add up all the masses of each type of atom in the compound. • Example: Molar Mass of Ca(OH)2 Ca: 1 x 40 = 40 O: 2 x 16 = 32 The molar mass is the H: 2 x 1 = 2 sum (40 + 32 + 2) which is equaled to 74 g/mol

  7. Molar Mass • Is the mass of 1 mole of a per substance • Has units of grams per mole (g/mol) • Equaled to the atomic mass of the element or compound.

  8. Calculations:Converting moles to grams • Given # of mole X g (look at periodic table)= g of 1 mole • How many grams of lithium are in 3.50 moles of lithium? • 3.50 mole X 6.941 g = 24.29 g Li 1 mol

  9. Calculations:Converting grams to moles • Given # of g X 1 mol = mol of g (look at periodic table) • How many moles of lithium are in 18.2 grams of lithium? • 18.2 g X 1 mol Li = 2.622 mol Li 6.941 g

  10. Calculations:Converting Moles to Particles • Given # of mol x 6.02 x 1023 part= atoms 1 mol • How many atoms/particles/molecules of lithium are in 3.50 moles of lithium? • 3.50 mole X 6.02 x 1023 = 2.11 x 1024 atoms of Li 1 mol

  11. Calculations:Converting Particles to Moles • Given # of particles x 1 mole = mol 6.02 x 1023 • How many moles of lithium are there in 1.2044 x1024 particles of Li? • 1.2044 x 1024 part x 1 mole = 2.0 mol Li 6.02 x 1023 part

  12. Calculations:Converting grams to particles • Given # of grams x 1 mol x 6.022 x 1023= particles ? g 1 mol • How many atoms/particles/molecules of lithium are in 18.2 g of lithium? • 18.2 g x 1 mol x 6.022 x 1023 = 1.58 x 1024 particle Li 6.941g 1 mol

  13. Calculations:Converting particles to grams • Given # of particles x 1 mol x ? g = g 6.022 x 1023 1 mol • How many grams are there in 8.02 x 1025 particles of lithium? How many grams of lithium are in 3.50 moles of lithium?

  14. How many grams of lithium are in 3.50 moles of lithium? How many moles are in 9.8 grams of NaCl? How many ions/atoms/particles are in 5.0 moles of H2O? How many moles are in 7.8 x 10 27 particles of Cu?

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