Name Lab Partner(s) Copper Odyssey Chemical Reactions of Copper Date Period Elemental copper metal will be converted into copper (II) ion and then brought through a series of compound conversions until the copper is returned to its original form as a metal. The conversions will illustrate various types of chemical reactions including single displacement reactions, double displacement reactions, neutralization reactions, oxidation-reduction reactions, and decomposition reactions. The reactions will also demonstrate the evolution of a gas, the generation of heat, and the formation of a precipitate. The purpose of this experiment is to observe each of the conversions and then write balanced equations for each reaction. By noting the nature of the changes, the proper phase notation can be added to the equations. When the original mass of the copper is compared to mass of the copper recovered, the Law of Conservation of Mass can be verified. WEAR SAFETY GOGGLES THROUGHOUT THIS LAB! PROCEDURE: CONVERSION I 1) Clean, dry, and label a 100 ml beaker (or larger beaker if none is available). Determine its mass to the nearest 0.01 gram. Record. 2) Obtain approximately 0.5 grams of copper turnings, place in the beaker and determine the mass of beaker plus copper to the nearest 0.01 grams. Record. 3) In a location with good ventilation or in a fume hood, carefully add 10 ml of 6M nitric acid solution (CAUTION!) to the copper using the graduations on the beaker. As you add the nitric acid to the copper, a poisonous gas will be produced. Be careful not to breathe the gas. Place watch glass on top of the beaker. Note the nature of the two reactants and any products which form. 4) Leave in well ventilated location until the copper is completely dissolved and the brown gas ceases to be produced. 5) The word equation for the Conversion I reaction is: copper + nitric acid -> copper (II) nitrate + nitrogen dioxide + water Write and balance the formula equation for this reaction with proper phase notation.
CONVERSION II 6) Obtain your beaker and test the blue solution with ph paper as indicated by the lovely Mrs. Simms. Record value. 7) Using the graduations on a 50 ml beaker, obtain 10 ml of 6M sodium hydroxide solution. (CAUTION!) Test the solution with ph paper as before. Record value. 8) Fill a 250 ml beaker 1/3 full of ice water. Carefully place the 100 ml beaker containing the Conversion I solution inside the 250 ml beaker so the beaker floats in the water. 9) Cautiously and slowly, pour the 10 ml of sodium hydroxide solution down the stir rod into the blue copper(ii) nitrate solution in the 100 ml beaker. Stir gently with a glass stirring rod. Considerable heat is generated by this reaction. 10) Test the resulting solution with ph paper. If this ph test does not match the original color of the sodium hydroxide solution, add additional sodium hydroxide solution, a little at a time, while mixing until it does. Note color of the solid that forms. Rinse the 50 ml beaker with water. 11) The reaction between the excess nitric acid solution from Conversion I and the sodium hydroxide solution is an acid/base neutralization reaction which produces water and soluble sodium salt. Write the word equation for this reaction. 12) Write and balance the formula equation for the reaction in #11 using the proper phase notation. 13) After the sodium hydroxide solution neutralizes the excess acid, the sodium hydroxide solution reacts with the copper (II) nitrate in a double displacement reaction. The new copper compound is insoluble and forms a precipitate. The other salt is soluble and remains in solution. Write the equation for this reaction. 14) Write and balance the formula equation for the reaction in #13 using the proper phase notation. CONVERSION III 15) Add distilled water to the beaker to the 60 ml mark. Heat on hot plate to a gentle boil and stir until all the material is converted to a black-brown substance. This substance is copper (II) oxide. 16) Remove the beaker from the hotplate, using beaker tongs, and let cool on an insulating pad for 5 minutes. This wait will allow the black precipitate to settle. Pour off the clear liquid on the top into a 250 ml beaker. Try not to lose any of the black solid. 17) To rinse the black solid, add 50 ml of distilled water to the beaker. Stir gently. Let the precipitate settle for another 5 minutes and pour off the wash water into the same 250 ml beaker, again leaving all solid particles in the 100 ml beaker. Discard the rinse water in the 250 ml beaker. 18) The conversion of copper(ii) hydroxide to copper (II) oxide is a decomposition reaction, where water is driven out of the copper(ii) hydroxide with heat. Write the word equation for this reaction. 19) Write and balance the formula equation for the reaction in #18 using proper phase notation.
CONVERSION IV 20) Add 20 ml of 3M sulfuric acid (CAUTION!) to the black copper(ii) oxide in the beaker. Stir gently. The oxide should dissolve within a minute or so. If necessary, heat gently on a hot plate to enhance the dissolving process. Do NOT get the solution hot or let boil! Note color of product. 21) When an acid reacts with an oxide, a salt and water form. Write the word equation for the Conversion IV reaction. 22) Write and balance the formula equation for the reaction in #21 using proper phase notation. CONVERSION V 23) Using a plastic weigh boat, obtain 2-3 grams of granular zinc (no need to record the mass). Slowly add the zinc to the copper(ii) sulfate solution which resulted from the last conversion and immediately cover the beaker with a watch glass. 24) Allow the beaker to stand as the reaction proceeds. Occasionally, stir the reaction mixture with a stirring rod to break up the clump of copper metal which forms. Make observations on the nature of the reaction. 25) For the reaction to be complete, all the blue color should disappear and all the excess zinc should dissolve. If all the blue color has not disappeared, add a few more granules of zinc. If all the zinc has not reacted, add approximately 10 ml more sulfuric acid. 26) Let the beaker stand until the zinc metal completely disappears. Since the reaction produces hydrogen gas, the absence of bubbles will indicate when the zinc metal is all consumed. Again, break up any clumps of copper and then let the beaker stand until the copper settles out. 27) Decant off the clear liquid into the same 250 ml beaker used before. (To decant a mixture of liquid and solid, pour off the liquid into another container, making sure not to pour away any of the solid at the bottom of the beaker.) Wash the copper in the beaker two times with 20 ml portions of tap water and then a third and final time with distilled water. Stir vigorously, let settle, and decant the wash water each time into the 250 ml beaker. Don t lose any copper. Discard wash water. 28) Place the beaker with the copper into the drying oven to gently dry the copper product. Leave in overnight. 29) Remove the beaker from the drying oven and allow to cool on an insulating pad if needed. 30) Determine the mass of the beaker plus copper and record. Deposit the copper in the container provided. Clean, dry, and return the 100 ml beaker. 31) There are two reactions occurring in this conversion: the single displacement reaction of zinc reacting with copper sulfate solution, and the single displacement reaction of zinc reacting with sulfuric acid. Complete the word equation for both these reactions. 32) Write and balance the two formula equations for reactions in #31 using proper phase notation.
Name Lab Partner(s) Copper Odyssey Lab Data Date Period Table I. Qualitative Data Substance Formula Color Phase Copper Nitric acid Copper (II) nitrate Nitrogen dioxide Sodium hydroxide Copper (II) hydroxide Copper (II) oxide Sulfuric acid Copper (II) sulfate Zinc Zinc sulfate Hydrogen gas Table II. Quantitative Data Mass of the 100 ml beaker Mass of the beaker and the copper at start Starting mass of copper solid Final mass of copper solid % of copper recovered ph reading from Conv. II step 6 ph reading from Conv. II step 7
Analysis: Use the lab directions, labeled chemical bottles, ion chart, textbook, and your own knowledge of chemistry to complete this section. 1. Write balanced equations with state-of-matter symbols (phase notation) for each conversion of copper as indicated in the lab directions. CONVERSION I CONVERSION II CONVERSION III CONVERSION IV
CONVERSION V 2. Determine the percent recovery of copper. % recovery = Final copper mass x 100 Starting copper mass Conclusion: 1. Complete the following flow diagram for the chemical changes which occurred to the copper sample during the conversions in this lab. Use your equations above as a guide. Show both name and formula. COPPER 4 COPPER NITRATE 4 2. What is the Law of Conservation of Mass? Based on the flow diagram above and the result of the % recovery of copper, how does this experiment relate to the Law of Conservation of Mass? Use complete sentences to answer these two questions.