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Stoichiometry: Chemical Reactions are like Recipes

Stoichiometry: Chemical Reactions are like Recipes. How much reactant is needed to make a certain amount of product?. Dozen = 12. Case = 24. Ream = 500. Units. A dozen eggs = 12 eggs A case of coke = 24 cans A ream of paper = 500 sheets A century = 100 years In Chemistry, we use…

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Stoichiometry: Chemical Reactions are like Recipes

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  1. Stoichiometry: Chemical Reactions are like Recipes How much reactant is needed to make a certain amount of product?

  2. Dozen = 12 Case = 24 Ream = 500

  3. Units • A dozen eggs = 12 eggs • A case of coke = 24 cans • A ream of paper = 500 sheets • A century = 100 years In Chemistry, we use… Mole: It is a unit equal to 6.022 x 1023 atoms or molecules This number is called Avogadro’s Number, in honor of Amadeo Avogadro.

  4. How Big is a Mole? -One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles. -One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 million times.

  5. Molar Mass • Molar Mass: The mass of 1 mole of substance. • 1 mole of carbon contains 6.022 x 1023 atoms and has a mass of 12.0107 grams. • Unit: g/mol • Carbon’s molar mass is 12.01 g/mol

  6. Molar Mass ZnCl2: 1 Zn: 1 x 65.39 g/mol = 65.39 g/mol 2 Cl: 2 x 35.45 g/mol = 70.90 g/mol Molar Mass: 136.29 g/mol

  7. Molar Mass ZnSO4: 1 Zn: 1 x 65.39 g/mol = 65.39 g/mol 1 S: 1 x 32.07 g/mol = 32.07 g/mol 4 O: 4 x 16.00 g/mol = 64.00 g/mol Molar Mass = 161.46 g/mol

  8. General Plan for Converting Mass, Amount, and Number of Particles Use Avogadro’s Number Use the molar mass Amount of Substance in Moles Number of Atoms or molecules Mass of substance (grams)

  9. Sample Problem 1. A chemist has a jar containing 388.2 g of iron. How many moles of iron does the jar contain?

  10. Sample Problem 2. A student needs 0.366 mol of zinc for a reaction. What mass of zinc in grams should the student use?

  11. Sample Problem 3. How many moles of lithium are there in 1.204 x 1024 lithium atoms?

  12. Chemical Equations are like Cooking Recipes

  13. “Mole Ratio” of eggs to cookies Recipe makes 5 dozen cookies. 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Velasquez has 5 eggs. How many dozens of cookies can she make? 5 eggs 5 doz. 2 eggs = 12.5 dozen cookies Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  14. “Mole Ratio” of eggs to cookies Recipe makes 5 dozen cookies. 2 1/4 c. flour 1 tsp. baking soda 1 tsp. salt 1 c. butter 3/4 c. sugar 3/4 c. brown sugar 1 tsp vanilla extract 2 eggs 2 c. chocolate chips Henkels has 9 cups of chocolate chips. How many dozens of cookies can he make? 5 eggs 5 doz. 2 eggs = 12.5 dozen cookies Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

  15. “Mole Ratio” “Mole Ratio” Proportional Relationships: S’more Activity 2 Gc + 1 M + 4 Cp  1 Sm If each student is to make one S’more, and I have 30 students, how many graham crackers & chocolate pieces will I need? Given: 30 S’mores Unknown: ? Gc, ? Cp 30 S’mores 30 S’mores 2 Gc 1 S’more 4 Cp 1 S’more = ? = ?

  16. Stoichiometry Diagram Given Unknown Substance A Substance B Mass Mass Use periodic table 1 mole = molar mass (g) Use periodic table 1 mole = molar mass (g) Mole Ratio Use coefficients from balanced chemical equation Volume Mole Volume Mole 1 mole = 22.4 L STP 1 mole = 22.4 L STP (gases) (gases) 1 mole = 6.022 x 1023 particles (atoms or molecules) 1 mole = 6.022 x 1023 particles (atoms or molecules) Particles Particles

  17. Mole Ratio 2Al2O3(l) 4Al(s) + 3O2(g) 2 molecules 4 atoms 3 molecules 2 dozen 4 dozen 3 dozen 2 moles 4 moles 3 moles -The coefficients of this equation tells us that for every 2 moles of aluminum oxide, it produces 4 moles of solid aluminum and 3 moles of oxygen molecules. -The mole ratio, a conversion factor between two amounts in a chemical reaction. It is indicated by the coefficients of the chemical equation. Mole Ratios: 2 mol Al2O3 4 mol Al 4 mol Al 2 mol Al2O3 2 mol Al2O3 3 mol O2 3 mol O2 2 mol Al2O3

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