1. Drill – Empirical/Molecular Formulas Drill Please complete #1 and #2

2. Agenda Pass fwd empirical/molecular form WS Limiting Reactants WS Reminder: Mole Project due Mar 18 Stoichiometry Test - Friday

3. Limiting Reactants

4. Example Your job is to attach arms on dolls in a doll factory. If you have 600 arms and 350 dolls, how many finished dolls can you make? What do you have in excess? What is limiting your production – the arms or the dolls?

5. Reagent = reactant Limiting Reactant – the reactant that is completely consumed. This reactant limits the amount of product that is formed. Excess Reactant – the reactant that is not limiting the reaction. There will be leftovers of this reactant.

6. How to solve for limiting reactant 1.Write the balanced chemical equation 2.Determine the moles of each reactant 3.Determine how many moles of product each reactant would make using a mole ratio 4.The reactant that yields less product is the limiting reactant.

7. Start here pd 3

8. 1.Write the balanced chemical equation Copper reacts with sulfur to form copper (I) sulfide. What is the limiting reagent when 80.0g Cu reacts with 25.0g S? CuS+  Cu 2 S2

9. 2.Determine the moles of each reactant. Copper reacts with sulfur to form copper (I) sulfide. What is the limiting reactant when 80.0g Cu reacts with 25.0g S? 80.0 g Cu x 25.0 g S x 1 mole Cu 1 mole S 63.55 g Cu 32.06 g S = 1.26 mol Cu =.780 mol S

10. 3.Determine how many moles of product each reactant would make using a mole ratio Copper reacts with sulfur to form copper (I) sulfide. What is the limiting reactant when 80.0g Cu reacts with 25.0g S? 1.26 mol Cu x.780 mol S x 1 mol Cu 2 S 2 mol Cu 1 mol S =.630 mol Cu 2 S =.780 mol Cu 2 S 1 mol Cu 2 S

11. 4.The reactant that yields less product is the limiting reagent. Copper reacts with sulfur to form copper (I) sulfide. What is the limiting reactant when 80.0g Cu reacts with 25.0g S? Copper yields.630 mol Cu 2 S Sulfur yields.780 mol Cu 2 S So Copper is the limiting reagent

12. Amount of Excess? In order to determine how much (mass) of excess reactants there are, you must figure out what mass of the excess reactant got used up…then subtract that from the initial mass.

13. Amount of Excess? Step 1 – Start with moles of product formed (from limiting reactant). Step 2 – Convert back to moles of excess reactant. Step 3 – Convert from moles to mass of excess reactant. Step 4 – Subtract this value from the original mass of excess reactant (given in problem)

14. Start here – pd 4B

15. Sample Problem 3 Fe + 4 H 2 O Fe 3 O 4 + 4H 2 –When 36.0 g of water is mixed with 67.0 g of Fe, which is the limiting reactant? –Determine the grams of iron oxide produced. –Determine the mass of excess reactant remaining.

16. 1.Convert both masses to moles and calculate the number of moles of Fe 3 O 4 67.0 g Fe = 0.400 mol Fe 3 O 4 36.0 g H 2 0 = 0.499 mol Fe 3 O 4 2. Convert back to mass of excess reactant 0.400 mol Fe 3 O 4 x 4 mol H 2 0 x 18.02 g H 2 0 = 1 mol Fe 3 O 4 1 mol H 2 0 28.8 g H 2 0 3. Subtract this value from the original mass of excess reagent (given in problem) 36.0 g H 2 O – 28.8 g H 2 O consumed = 7.2 g H 2 O remaining

17. Homework Mole Project Limiting Reactant Worksheet

18. Pd 4a – start here

19. Agenda Stoichiometry Test Hydrates with Worksheet Stochiometry Lab Data

20. Hydrates When salts combine chemically with water and form unstable hydrated crystals Although in a chemical bond, this water of hydration maintains its characteristic composition Instead of H 20 Na 2 SO 14, we write Na 2 SO 4 H 2 O

21. Homework Hydrates WS Stoichiometry Test

22. Drill – pd 3 Determine the percentage of water in the following hydrate: Sc(NO 3 ) 3 · 10H 2 O [scandium(III) nitrate decahydrate]

23. Answer 43.8% water

24. Drill – all classes In an experiment, 3.25 g of NH 3 are allowed to react with 3.50 g of O 2. NH 3 + O 2 NO + H 2 O a. Which reactant is the limiting reagent? b. How many grams of NO are formed? c. How much of the excess reactant remains after the reaction?

25. Drill – all classes In an experiment, 3.25 g of NH 3 are allowed to react with 3.50 g of O 2. NH 3 + O 2 NO + H 2 O a. Which reactant is the limiting reagent? O 2 b. How many grams of NO are formed? 2.63 g NO c. How much of the excess reactant remains after the reaction? 1.71 g NH 3 left

26. Make sure to turn in : Composition of Hydrates WS Limiting Reactants WS Lab Calculations

27. Next class Wear close-toed shoes – Lab Wed or Th will be your test Does anyone need a mole pattern?

28. Agenda Lab Calculations Mixed Stoichiometry/Limiting Reactants WS Review Sheet if finished

29. Drill Read the Introduction of Lab Change Lab to read Percent Composition of Epsom Salt

30. Lab Only heat crucible once for 10 minutes Allow it to cool for 10 minutes Make sure crucible is cool before handling it.

31. Lab Groups – pd 4B 1.Stephanie, Chris H. 2.Ben, Comfort 3.Jessica, Zach 4.John, Chris J 5.Sahra, O 6.Amelia, Valentina 7.Emileigh, Caine 8.Troy, Claire,Max 9.Shivani, Anjali 10.Josh, Becky 11.Sophia, Max 12.Joey, Alexis

32. Homework Review WS