The Activity Series of Metals

Limiting Reactant and Percentage Yield in a Chemical Reaction

Introduction: Reactants in any reaction must react in proportions that are dictated by their coefficients in the balanced reaction. This relationship is based on a mole ratio and not on mass. Reactants that are in lesser amounts will be the limiting reactant and will determine how much product should be theoretically produced. For reactions carried out in the lab, the actual yield of the product is often less than the theoretical yield. The difference between the actual yield and the theoretical yield is calculated as a percentage yield. In this lab you will be studying the reaction of aluminum foil with aqueous copper (II) chloride to determine the limiting reactant and percentage yield based on the stoichiometric relationship.

Lab Report Details Title Block and Purpose Complete a title block at the top of your page and record the purpose of the lab. Quantitative Observations Draw and properly title Table 1 for your quantitative observations. Table 1 should contain mass of beaker 1, mass of beaker 1 and CuCl2 , mass of CuCl2 , mass of aluminum, mass of beaker 1 and Cu, mass of Cu. Include Trial 1, 2, 3, and an average row. You will complete Trial 1. Trials 2 and 3 will be done by other groups. Qualitative Observations Draw and properly title Table 2 for your qualitative observations. Table 2 should contain a physical description (colour, clarity state) of the reactants (before the reaction) and a description of the products (after the reaction). Calculations and Analysis Answer the analysis questions and hand in the rubric with your lab report.

Materials Apron and goggles Retort stand copper (II) chloride 150mL beaker 1 Wire gauze Heavy duty Aluminum foil Stirring rod Crucible tongs (6 cm X 10 cm strip) Ruler Forceps (tweezers) Clean beaker for waste Bunsen burner 50 mL graduated cylinder Ring clamp Watch glass

Procedure 1. Carefully read over the procedure and create your data table using the proper format. 2. Put on your apron and safety goggles. DO NOT take them off until the lab is done. 3. Obtain your materials. Clean and dry all equipment. 4. Add 2 g (or slightly less) of copper (II) chloride to beaker 1. Record the exact mass including all available significant digits in Table 1. 5. Add 50.0 mL of water to beaker 1. Stir to dissolve. 6. Fold the aluminum foil lengthwise once and again to make a 1.5 cm X 10 cm strip. 7. Coil the foil into a circle and lay on the bottom of the beaker with the copper chloride solution so that the aluminum is submerged. 8. Clamp the iron ring on the stand and place the beaker on the wire gauze (on the iron ring). 9. Heat GENTLY with the burner for 5 minutes. Ensure a slow boil. Reduce heat if foaming develops. 10. Turn off the burner and allow the solution to cool until you can hold it in your hands. 11. Using the forceps, carefully shake the foil to dislodge the copper from it. Make sure all copper lands in beaker 1. 12. Put the remaining aluminum foil in a clean waste beaker and pick out any copper pieces and return them to beaker 1. 13. Add 50 mL of water to beaker 1 and stir well to wash the copper. Discard most of the water into your waste beaker without losing any copper pieces. If you lose some copper, pick it out of your waste beaker and return it to beaker 1. 14. Repeat another wash. 15. Spread the copper pieces on the bottom of beaker 1 with the stir rod. 16. Cover the beaker with a watch glass (convex side down) and heat GENTLY to evaporate any water. 17. When it appears dry, remove the watch glass with the crucible tongs and heat gently for 3 more minutes. Make sure the copper does not turn black, reduce heat! 18. Place a dry cooled watch glass back on top. If condensation appears on the bottom of the watch glass, continue to heat to remove the water. 19. Repeat steps 18 and 19 until no more condensation appears. Turn off the burner and let cool. Never put a hot beaker on the balance. 20. Determine the mass of the beaker and copper. 21. Clean up your work area and return all the cleaned materials back to their place. Wipe down your lab bench with soapy water. 22. Obtain data from two other groups for Trial 2 and 3. Analysis 1. a) What type of reaction occurred? b) Write the balanced chemical equation including states. 2. a) Which reactant was in excess? What observation(s) indicated this? b) Which is the limiting reactant? What observation(s) indicated this? 3. Calculate the following showing all steps and units. a) Limiting Reactant. Use the average mass of Al from the 3 trials and the average mass of copper(II) chloride from the 3 trials. b) Theoretical Yield. Use the limiting reactant to calculate the theoretical mass of copper produced. c) Experimental Yield. Calculate the average mass of copper produced in this reaction. d) Percent yield. Use the theoretical and experimental yield for this experiment to find percent yield. 4. Did you expect your percent yield to be exactly 100%? 5. What types of errors could have contributed if your percent yield was less than 100%? 6. Explain what types of errors could have contributed if your percent yield was more than 100%.

SCH-3U Stochiometry and Percentage Yield in a Chemical Reaction

Communication Title Block /2 -Clear, neat, well organized. -Contains an appropriate title, dates, name and partner’s name. Purpose /2 Appropriate general purpose is given in one or two sentences.

Results - Data Tables /14 - Appropriate titles at the top - Well organized and neat (numbers are aligned) - Units are in the headings - Contains all relevant data and observations Overall clarity, neatness, spelling and grammar /2

Overall Communication /20 Inquiry Experimental Technique reflected by the significant digits /2 shown and the accuracy of the results Analysis Question 1 /7 Balanced chemical reaction is complete Type of reaction identified Analysis Question 2 /5 Excess and limiting reactants correctly identified and explained using qualitative and quantitative observations Analysis Question 3 /12 Limiting reactant, (4) theoretical yield, (4) experimental yield and (2) percent yield (2) are calculated correctly showing all steps and units Analysis Question 5 /4 Accuracy and precision, sources of error and ways to improve the experiment are discussed in a short paragraph

Overall Inquiry /30