2. Stoichiometry Unit 6

3. Topic 1 Intro / mole to mole

4. 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?

5. Basic Stoichiometry 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. Al 2 O 3 Al + O 2 243

6. Basic Stoichiometry 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? Al 2 O 3 Al + O 2 243 4343

7. Writing Mole Factors 4 Fe + 3 O 2 2 Fe 2 O 3 Fe and O 2 4 mole Fe and 3 mole O 2 3 mole O 2 4 mole Fe Fe and Fe 2 O 3 4 mole Feand2 mole Fe 2 O 3 2 mole Fe 2 O 3 4 mole Fe O 2 and Fe 2 O 3 3 mole O 2 and 2 mole Fe 2 O 3 2 mole Fe 2 O 3 3 mole O 2

8. Learning Check S1 3 H 2 (g) + N 2 (g) 2 NH 3 (g) A. A mole factor for H 2 and N 2 is 1) 3 mole N 2 2) 1 mole N 2 3) 1 mole N 2 1 mole H 2 3 mole H 2 2 mole H 2 B. A mole factor for NH 3 and H 2 is 1) 1 mole H 2 2) 2 mole NH 3 3) 3 mole N 2 2 mole NH 3 3 mole H 2 2 mole NH 3

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

10. Example 4 Fe + 3 O 2 2 Fe 2 O 3 Given Unknown How many moles of Fe 2 O 3 are produced when 6.0 moles O 2 react? 6.0 mole O 2 2 mole Fe 2 O 3 = 4.0 mole Fe 2 O 3 3 mole O 2

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

12. Solution 4 Fe + 3 O 2 2 Fe 2 O 3 12.0 mole O 2 4 mole Fe = 16.0 mole Fe 3 mole O 2

13. Practice 2 4 Fe + 3 O 2 2 Fe 2 O 3 How many moles of O 2 are needed to produce 0.400 mole of Fe 2 O 3 ?

14. Topic 2 Mass to mole or mole to mass

15. 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

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

17. Solution 0.400 mole Fe 2 O 3 3 mole O 2 32.0 g O 2 2 mole Fe 2 O 3 1 mole O 2 = 19.2 g O 2

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

19. Unit 6 Topic 3 Mass to mass conversion

20. 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

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

22. 2 H 2 (g) + O 2 (g)2 H 2 O (g) Start w/ grams given 1 mole of given Molar mass of Given(g) Moles of “unknown” (coefficient) Moles of given (coefficient) Molar mass of “unknown” 1 mole “unknown” grams “unknown” = given unknown g H 2 O mole H 2 O mole O 2 g O 2

23. 13.1 g H 2 O 1 mole H 2 O 1 mole O 2 32.0 g O 2 18.0 g H 2 O2 mole H 2 O 1 mole O 2 = 11.6 g O 2

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

25. Solution 4 Na + O 2 2 Na 2 O 50.0 g Na 1 mole Na 1 mole O 2 32.0 g 23.0 g Na 4 mole Na 1 mole O 2 = 17.4 g O 2

26. Practice Acetylene gas C 2 H 2 burns in the oxyactylene torch for welding. How many grams of C 2 H 2 are burned if the reaction produces 75.0 g of CO 2 ? 2 C 2 H 2 + 5 O 2 4 CO 2 + 2 H 2 O

27. Solution 2 C 2 H 2 + 5 O 2 4 CO 2 + 2 H 2 O 75.0 g CO 2 1 mole CO 2 2 mole C 2 H 2 26.0 g C 2 H 2 44.0 g CO 2 4 mole CO 2 1 mole C 2 H 2 = 22.2 g C 2 H 2

28. 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)