Procedure Reaction 1: Dissolving the Copper 1. Obtain a clean,dry, glass centrifuge tube. 2. Place a piece of copper wire in aweighing paper, determine the mass of the wire and place it in thecentrifuge tube. The copper wire should weigh less than 0.0200grams. 3. In a fume hood, add seven drops of concentrated nitricacid to the reaction tube so that the copper metal dissolvescompletely. Describe your observations in the lab report. (Caution,Concentrated nitric acid and nitrogen dioxide are very corrosive.Either will turn your skin yellow on contact. Do not leave anyspills on the lab bench or in the fume hood.) 4. When the copperhas dissolved, add seven drops of distilled water to the tube.Reaction 2: Preparation of Copper(II) Hydroxide 1. Add 15 drops of3.0 M aqueous sodium hydroxide to the tube. Make sure that thereactants are well mixed. Shake the tube carefully or gently flickthe bottom of the tube with your finger. Remember that the contentsof the tube may still be corrosive. 2. Add a second 15 drops ofNaOH(aq), mix well, and record your observations. If you have twolayers at this point it means that you have not mixed the solutionwell enough. 3. Centrifuge the reaction mixture. 4. The liquid atthe top of the centrifuged mixture is called the supernatant whilethe solid is called a precipitate. Before separating thesupernatant from the precipitate it is necessary to ensure that allof the copper(II) hydroxide has been precipitated. The supernatantshould be clear and colorless indicating the absence of any Cu+2ions in the solution. It should also be basic due to an excess ofOH- ions. Using a clean glass stirring rod, transfer a drop of thesupernatant onto a piece of red litmus paper. If the litmus paperturns blue then the solution is basic and enough NaOH has beenadded. If the paper does not turn blue, add more NaOH, mix well,recentrifuge, and repeat the litmus paper test until the paper doesturn blue. 5. An efficient separation of supernatants andprecipitates is key to obtaining a good final yield of copper. Thesupernatant liquid can be separated from the precipitate byexpelling the air from the bulb of a Pasteur pipet, inserting thetip of the pipet into the supernatant, then gently sucking thesupernatant into the pipet. If you expel air or liquid into theprecipitate with the pipet, you will stir up the precipitate andwill have to repeat the centrifugation step. Remove as much liquidas possible and discard it in the waste container provided on theinstructor’s cart. It is better to leave a small amount ofsupernatant liquid than to remove some of the copper(II) hydroxideprecipitate. Reaction 3: Formation of Copper(II) Oxide 1. Set up ahot water bath by placing a beaker of water on a hotplate, placingan iron ring around the beaker, and heating the water to boiling.2. Place the centrifuge tube containing the copper(II) hydroxideinto the boiling water. Carefully hold the tube with a test tubeclamp so that it doesn’t get water into it. Record yourobservations. Reaction 4: Formation of Copper(II) Sulfate 1. Add 20drops of 3.0 M H2SO4 to the solid in the centrifuge tube. Stircarefully to ensure that the copper(II) oxide dissolves completely.Complete dissolution of the mixture will require thorough mixingand possibly heating of the solution. 2. Obtain the mass of asmall, clean, glass test tube as accurately as possible. 3.Transfer the liquid from the centrifuge tube into the test tube.Rinse the centrifuge carefully with 1.0 mL of distilled water andtransfer the rinse into the test tube containing your sample. 4.Record your observations on the data sheet. Reaction 5: Formationof Copper Metal 1. Add a small quantity of zinc powder to thesample solution. Continue adding zinc in small quantities until thesolution loses the blue copper(II) color. Any excess zinc addedwill need to be removed so don’t add it too quickly or in largequantities. When the solution has turned colorless, add severaldrops of 3.0 M H2SO4 to the tube to dissolve any left over zinc.You can tell that the zinc has dissolved when addition of sulfuricacid does not generate bubbles. 2. Allow the copper metal to sinkto the bottom of the tube and carefully remove the supernatantliquid using a Pasteur pipet. 3. Wash the red-brown copper metal inthe tube with 1.0 mL of water. Allow the copper metal to settle tothe bottom and remove the excess water. Repeat this rinsing processtwo more times. 4. Describe your observations on the data sheet.Drying the copper metal 1. After removing as much of the thirdrinse water as possible you are ready to dry the metal. This mustbe done carefully in a cool Bunsen Burner flame. If the tube isheated too quickly there is a risk of ejecting the contents of thetube as the water boils. Also, if the flame is too hot you mayconvert the copper metal back into black copper(II) oxide. Theobjective is to drive the water from the tube as steam. Make surethat as water condenses on the walls of the tube that you continueto heat until all of the water if gone from the tube. 2. Once allof the water is removed from the tube, cool the tube and itscontents then determine the mass of copper by weighing the tube andsubtracting the tube + copper weight from the weight of the emptytube (Reaction 4 step 2). If the mass of copper is higher than theoriginal mass of the copper wire it either contains water or zincor has been converted to copper(II) oxide. Excess water can beremoved by reheating the tube and reweighing to constant mass.Excess zinc requires addition of sulfuric acid followed byre-rinsing with water and re-drying. Chemistry 1215 Experiment 9Lab Report Name ______________________________ Data Sheet Mass ofcopper wire _______________ Mass of clean, dry test tube_______________ Mass of test tube plus copper _______________ Massof final copper sample _______________ Percent recovery of copper.Show all calculations. Observations 1. Describe your observationsfor Reaction 1 including colors, gases formed, etc. 2. Describeyour observations for Reaction 2 including colors, gases formed,etc. 3. Describe your observations for Reaction 3 including colors,gases formed, etc. Estimate the temperature of the decomposition ofCopper(II) hydroxide. 4. Describe your observations for Reaction 4including colors, gases formed, etc. 5. Describe your observationsfor Reaction 5 including colors, gases formed, etc. Write a briefdiscussion of your results including a statement of the finalpercent recovery of copper and a discussion of reasons why therecovery differs from 100%. Chemistry 1215, Experiment #9; Copperand its compounds, Pre-lab Name____________________________________ 1. Write a balanced chemicalequation including phase labels for the reaction between aqueouscopper (II) nitrate and aqueous sodium hydroxide. 2. Nitrogenmonoxide (NO) and nitrogen dioxide (NO2) are toxic, corrosive gasesthat significantly lower blood pressure when inhaled. How are thesegases produced in today’s experiment? What should you do to protectyourself against their toxicity? 3. Iron reacts with oxygen fromthe atmosphere to produce iron (III) oxide, also known as rust(Fe2O3). What chemical species is oxidized in this reaction? Whatis the reducing agent? Jaffrey Zagnut couldn’t find any nitric acidso he tried to dissolve his copper sample in hydrochloric acidinstead. Unfortunately his copper wouldn’t dissolve in HCl. Whywill copper dissolve in nitric acid but not in hydrochloric acid(after all, HCl is a stronger acid than HNO3). Chemistry 1215,Experiment #9; Copper and its compounds, Post-lab Name____________________________________ 1. Copper (II) hydroxide isconverted into copper (II) oxide by heating the test tubecontaining Cu(OH)2 in a hot water bath. Is it necessary to usedistilled water in this water bath? Why or why not? 2. Copper metaldoesn’t “rust” in the presence of oxygen at room temperature.However, it will react with O2 at elevated temperatures. Write abalanced chemical equation describing the formation of copper (II)oxide when copper metal is heated in air. 3. When zinc is dissolvedin sulfuric acid a gas is produced. What is the chemical identityof this gas? How is it produced? 4. Jaffrey Zagnut started with a0.032 g sample of copper which he took through the series ofreactions described in this experiment. At the end of theexperiment he obtained 0.038 g of a black product. What was hispercent yield? What is the most likely source of the error in hisexperiment? (Hint: consider question 2 above)