Turn in the following… Balancing Equations WS- Word Equation WS- 1 page WS Predicting Products Packet- tear off the last page…put your name on it!

You have 55 minutes to do the test… 2

3 Chapter 8- Stoichiometry Big, Scary name…. Just calculations chemists do!

4 Copper Series- Lab 1 Write and balance the equation for the reaction of copper (Cu) plus nitric acid (HNO 3 ) to produce Copper (II) nitrate (Cu(NO 3 ) 2 ) plus water (H 2 O) and nitrogen dioxide (NO 2 ). Cu + 4HNO 3 → Cu(NO 3 ) 2 + 2H 2 O + 2NO 2

5 Lab Concerns Use the same scales for each lab… they mass slightly different. Be sure to record any lab mistakes… too much reactant, lost product, other booboos. You will be calculating percent error and trying to explain the errors. You may never say that you made a mistake in your calculations-- there are 3 of you working, there should be no mistakes!

6 You will be working in groups of 3- be sure to exchange contact info and be sure to communicate if you will be absent. Jobs Rotate- Write you job at the top of each lab. 1. Leader- Keeps all on task and makes sure directions are followed. 2. Scientist- Follows directions and is in charge of making sure no mistakes occur. 3. Mathematician- insures calculations are correct. I will pick one lab per group to grade-- you get whatever score they get…make sure everyone in your group is completing the lab!

Procedure- Using the sharpie.. Put your period and lab station on the beaker. Ex: Determine the mass of your empty beaker. 2. Determine the mass of the copper. 3. Send your scientist to the stock room to put 20mL of HNO 3 into the beaker 4. Put on the watch glass and place on the hot plate in the fume hood. 7

Warm Up Check to be sure that you have the first 4 blanks of your Series 1 Lab complete. 8

9 Quantitative Analysis Composition stoichiometry- mass relationships of elements in compounds. Reaction Stoichiometry- involves mass relationships between the reactants and products in reactions

10 What do the coefficients mean? Mole Ratios Coefficients indicate the amount of each material (Moles or molecules) present in a reaction. C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O So… when looking at a balanced equation we can derive a whole set of conversion factors!

11 Ooh! Lets write a bunch!! C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O

12 Mole Ratio- The Definition… A conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction.

13 Mole Ratios allow us to do all sorts of cool calculations. Yipee! Ex: How many moles of CO 2 are produced when 0.38 mol C 6 H 12 O 6 are burned according to the following reaction? C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O

14 Mole to Mole Calculations…. Fe 2 O 3 + 3CO2Fe + 3CO 2 1. How many mol CO are necessary to react with 2.2 mol Fe 2 O 3 ? 2. How many mol Fe are produced if 1.8 mol CO is used?

15 Fe 2 O 3 + 3CO2Fe + 3CO 2 1. How many mol CO are necessary to react with 2.2 mol Fe 2 O 3 ?

16 Mole Ratios Fe 2 O 3 + 3CO2Fe + 3CO 2 b) How many mol Fe are produced if 1.8 mol CO is used?

17 Stoichiometric Conversions Congratulations! Now that you’ve mastered the only new conversion necessary for stoichiometry, We can convert our mole into other things using Stoichiometry!

18 Moles of AMoles of BMass of AMass of B Number of particles of ANumber of particles of B Volume of gaseous AVolume of gaseous B The following chart summarizes the conversions we can do:

19 So, can we use stoichiometry to determine the amount of product made in types of reactions lab? We used 0.2 g of CuCO 3 in the decomposition reaction. How much CuO was produced? CuCO 3 CuO + CO 2

20 Can we calculate how much carbon dioxide gas was produced? CuCO 3 → CuO + CO 2

21 Can we determine the amount of magnesium oxide produced in the synthesis reaction? We used about 0.5 g of Mg. Mg + O 2 MgO a. Balance the equation. b. Place the mass of Mg used in the upper left. c. Use DA to determine the theoretical mass of MgO.

22 Important Vocabulary Terms Theoretical yield- the maximum amount of product that can be produced from a given amount of reactant. Actual Yield- measured amount of a product obtained from a reaction (in lab).

23 What is the theoretical yield (in grams) of both products in the following reaction if 2.5 g of HCl is used? Zn + HCl ZnCl 2 + H 2 a. Balance the equation b. Put 2.5g HCl in the upper left c. Solve for g of zinc chloride. d. Solve for g of hydrogen.

Warm Up On your copper lab, #5 asks you to determine the theoretical yield for Cu(NO 3 ) 2. Do the calculation using your mass determined in #1. 24

Let’s make sure you are doing the other calculations correctly. 25

How did you do on the Mass – Mass WS? 26

27 There are a bunch of other calculations we can do using the flow chart… Moles of AMoles of BMass of AMass of B Number of particles of ANumber of particles of B Volume of gaseous AVolume of gaseous B

28 Stoichiometric Conversions How many grams of oxygen are produced when 17.5g of H 2 O 2 decompose according to the following equation? H 2 O 2 H 2 O + O 2 (Don’t forget to balance the equation!)

29 Stoichiometric Conversions How many liters of oxygen are produced when 17.5g of H 2 O 2 decompose according to the following equation? H 2 O 2 H 2 O + O 2 (Don’t forget to balance the equation!)

30 How many molecules of H 2 O 2 are needed to make 3.5 x molecules of water? 2H 2 O 2 2H 2 O + O 2

31 How many molecules of H 2 O 2 are needed to make 5.00 g of water? 2H 2 O 2 2H 2 O + O 2

32 Try these! CaCO 3 + Mg → MgCO 3 + Ca a) How many molecules of Ca are produced if 39.4g of MgCO 3 are also produced? b) How many grams of Mg are necessary to react with 0.97 mol CaCO 3 ?

Copper Lab- Series 2 1. Obtain the mass of your Cu(NO 3 ) 2 2. Add about 20 ml of distilled water. 3. Add 30 ml of NaOH 4. Obtain the mass of your filter paper!!! 5. Filter the mixture- rinse it well with distilled water. 6. Wash out your original beaker (check to be sure it is still marked with your period and lab station.) 33

34 Percent Yield In a perfect world, every student would get a perfect score on every test. Alas, we do not live in a perfect world How do we determine the score you got on the test?

35 Percent Yield (cont’d) In a perfect world, every reaction would produce the amount of material it is supposed to. Alas, we do not live in a perfect world. Percent yield = the ratio comparing the amount of material actually generated in a reaction to the maximum amount possible. Percent Yield = Actual Yield x 100 Theoretical Yield l

36 Percent Yield (cont’d) The theoretical yield is calculated using stoichiometry. The actual yield is found by experimentation. Key Point: You can never predict the actual yield or the percent yield.

Percent Yield 2Mg + O 2 → 2MgO 3.2 g of Magnesium reacted with excess oxygen. 4.9g of MgO was produced in the lab. Calculate the percent yield. 1. Balance Equation 2. Calculate Theoretical Yield 3. Calculate % Yield 37

38 Warm Up- Sb 2 S 3 (s) + 3Fe(s) 2Sb(s) + 3FeS(s) When 22.3g of Sb 2 S 3 reacts with excess of Fe, 12.7g Sb is produced in the lab. What is the percent yield?

Questions on the Homework? 39

Copper Lab- Series 3 The third reaction has copper (II) oxide and water being produced from copper (II) hydroxide. Write and balance the equation. What type of reaction is it? 40

Copper- Series 3 1. Determine the mass of the Cu(OH) 2. Don’t forget to subtract the mass of the beaker and filter paper! 2. Open up the filter paper containing your product and transfer as much of the copper hydroxide as you can into the large beaker. Put the filter paper in too. 3. Add 100 ml of distilled water. 4. Put the large beaker on the hot plate and heat to a gentle boil. 5. Use forceps to remove the filter paper 6. Use the squirt bottle to rinse the filter paper. 7. Decant as much water as possible. 8. Transfer back into your beaker. 9. Allow product to settle and decant more water. 41

Work on your calculations! 42

Warm Up The theoretical yield of CuO, calculated using stoichiometry was 45.3 g. The actual yield was 46.2 g. Determine the percent yield. Is the yield high or low? What could explain the yield? 43

44 Limiting / Excess Reagents Let’s think about a peanut butter sandwich… The recipe calls for 2 pieces of bread and 2 Tsp. of peanut butter. Write the reaction:

Now, we only have so much of each reactant… Huge tube o Skippy12 pieces of bread How many sandwiches can we make? 45

46 Limiting Reagent (cont’d) Chemical reactions are much the same way. The balanced chemical equation is the recipe, telling you how much of each thing you need. Often, chemicals are not mixed in the correct amounts, implying that one chemical will run out before the others. The chemical that runs out first is called the limiting reagent. The chemical that has some left over… is in excess. (The excess reagent)

47 Limiting Reagent (cont’d) a. Calculate the amount of reactant necessary to use up the given quantities (2 calculations). b. Compare what you have to what you need to determine limiting. c. Use the original amount to determine the maximum amount of products. d. Subtract what you use from what you have to determine amount of excess.

Limiting and Excess Calculations… Ex: 5.00g of HCl is mixed with 4.00g of NaOH according to the following reaction: HCl (aq) + NaOH (aq) → NaCl (aq) + H 2 O (l) 48

Limiting/Excess You react 54.8g of silver nitrate with 22.2g of calcium chloride according to the following rxn. AgNO 3 + CaCl 2 → AgCl + Ca(NO 3 ) 2 1. Balance the equation. 2. Determine the limiting. 3. Calculate the maximum amount of AgCl 4. Calculate the excess. 49