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Stoichiometry

Stoichiometry. Unit 6. Topic 1. Intro / mole to mole. Stoichiometry. Quantitative study of chemical reactions The basic question - how much? - is the object of stoichiometry .

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Stoichiometry

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  1. Stoichiometry Unit 6

  2. Topic 1 • Intro / mole to mole

  3. Stoichiometry • Quantitative study of chemical reactions • The basic question - how much? - is the object of stoichiometry. • Example: How many grams of silver chloride are produced when 17.0 grams of silver nitrate react with excess sodium chloride?

  4. Always starts with a balanced equation. From the balanced equation we can determine the molar ratios. Remember that the coefficients refer to the number of moles of each reactant or product there are in the balanced equation. So in this equation 2 moles of aluminum oxide decompose to form 4 moles of aluminum metal and 3 moles of oxygen gas. 2 4 3 Basic Stoichiometry Al2O3 Al + O2

  5. So for 2 moles of aluminum oxide, three moles of oxygen gas will be produced. Therefore, the molar ratio of aluminum oxide to oxygen gas would be 2:3 What would the ratio of aluminum metal to oxygen gas be? 2 4 3 Basic Stoichiometry Al + O2 Al2O3 4 3

  6. Writing Mole Factors 4 Fe + 3 O2 2 Fe2O3 Fe and O2 4 mole Feand 3 mole O2 3 mole O24 mole Fe Fe and Fe2O34 mole Fe and 2 mole Fe2O3 2 mole Fe2O3 4 mole Fe O2 and Fe2O3 3 mole O2 and 2 mole Fe2O3 2 mole Fe2O3 3 mole O2

  7. Learning Check S1 3 H2(g) + N2(g) 2 NH3(g) A. A mole factor for H2 and N2 is 1) 3 mole N22) 1 mole N2 3) 1 mole N2 1 mole H2 3 mole H2 2 mole H2 B. A mole factor for NH3 and H2 is 1) 1 mole H2 2) 2 mole NH3 3) 3 mole N2 2 mole NH3 3 mole H2 2 mole NH3

  8. 1. Mole-to-Mole conversion given Mole of A (coeff.)Mole of B (coeff.)Mole of A

  9. Example 4 Fe + 3 O22 Fe2O3 Given Unknown How many moles of Fe2O3 are produced when 6.0 moles O2 react? 6.0mole O22 mole Fe2O3 = 4.0 mole Fe2O3 3 mole O2

  10. Practice 1 4 Fe + 3 O2 2 Fe2O3 How many moles of Fe are needed to react with 12.0 mole of O2?

  11. Solution 4 Fe + 3 O2 2 Fe2O3 12.0 mole O24mole Fe = 16.0 mole Fe 3 mole O2

  12. Practice 2 4 Fe + 3 O2 2 Fe2O3 How many moles of O2 are needed to produce 0.400 mole of Fe2O3?

  13. Topic 2 • Mass to mole or mole to mass

  14. 2. Mole to Mass/Mass to Mole conversion mole of A (co) mole of B Molar mass of B (co) mole of A 1 mole of B Mass(g) of A 1mole A (co)mole of B molar mass of A (co) mole of A

  15. Example 4 Fe + 3 O2 2 Fe2O3 How many grams of O2 are needed to produce 0.400 mole of Fe2O3? What’s given? Moles of Fe2O3 What’s unknown? Grams of O2 Plan: Convert moles of Fe2O3 to moles of O2. Then convert moles of O2 to grams of O2.

  16. Solution 0.400 mole Fe2O33 mole O2 32.0 g O2 2 mole Fe2O3 1 mole O2 = 19.2 g O2

  17. Practice • 4 Fe + 3 O2 2 Fe2O3 • How many grams of Fe is needed to produce 0.400 mole of Fe2O3? • How many grams of Fe2O3 is produced from 5 moles of Fe and excess O2?

  18. Unit 6 Topic 3 • Mass to mass conversion

  19. 3. Mass to mass conversion Mass(g) of A 1mole A (co)mole of B molar mass(g) of B molar mass(g) of A (co) mole of A 1mole B

  20. Example The reaction between H2 and O2 produces 13.1 g of water. How many grams of O2 reacted? Write the equation H2 (g) + O2 (g) H2O (g) Balance the equation 2 H2 (g) + O2 (g) 2 H2O (g) Identify what’s given and what’s “unknown”

  21. given unknown Molar mass of “unknown” 1 mole of given Moles of “unknown” (coefficient) Molar mass of Given(g) 1 mole “unknown” Moles of given (coefficient) grams “unknown” = 2 H2 (g) + O2 (g) 2 H2O (g) Start w/ grams given g H2O mole H2O mole O2 g O2

  22. 13.1 g H2O 1 mole H2O 1 mole O2 32.0 g O2 18.0 g H2O 2 mole H2O 1 mole O2 = 11.6 g O2

  23. Practice How many grams of O2 are needed to react w/ 50.0 grams of Na in the reaction 4 Na + O2 2 Na2O Complete the set up: 50.0 g Na 1 mole Na 23.0 g Na

  24. Solution 4 Na + O2 2 Na2O 50.0 g Na 1 mole Na 1 mole O232.0 g 23.0 g Na 4 mole Na 1 mole O2 = 17.4 g O2

  25. Practice Acetylene gas C2H2 burns in the oxyactylene torch for welding. How many grams of C2H2 are burned if the reaction produces 75.0 g of CO2? 2 C2H2 + 5 O2 4 CO2 + 2 H2O

  26. Solution 2 C2H2 + 5 O2 4 CO2 + 2 H2O 75.0 g CO2 1 mole CO22 mole C2H226.0 g C2H2 44.0 g CO2 4 mole CO2 1 mole C2H2 = 22.2 g C2H2

  27. Pathways for Problems Using Equations Given (A) Unknown (B) grams (A) grams (B) molar molar mass (A) mass (B) coefficients moles (A) moles (B) Avogadro's Avogadro’s number number particles (A)particles (B)

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