Question

PartA: Penny-→ Cu2+(aq) Make sure it is dated prior to 1982. Record mass to nearest 0.001 I. Weigh a copper penny. grams. 2. Place 450 mL of distilled water in a clean 600-mL beaker. Place the beaker on a hotplate and heat until the water boils. Do not wait for the water to boil now, but proceed with the rest of the experiment. You will need this water for rinsing in step C3. CAUTION. You will generate poison°แs nitrogen dioxide gas in the next step. This step mแst be done under the hood. Keep hood glass pulled down and make sure vent fans are on. Watch for evidence of the reaction as the penny 'dissolves', the solution turas blue or green and the reddish-brown gas is evolved. 3. In a functioning hood, Place the penny in a 800 mL beaker and add 20 mL of concentrated nitric acid to the penny in the beaker. When the reaction is complete (the penny is gone and bubbles are being produced), slowly add 175 mL of distilled water to the beaker CAUTION Remember that you have concentrated nitric acid in the beaker and also that the beaker is hot due to the highly exothermic nature of the reaction above. If you spill any on your skin or clothing, wash immediately with water and get help immediately. Avoid breathing fumes. Part B: Cu(a)Cu(OH2() I. Slowly, add 180 mL of 3.0 M NaOH to the blue solution while stirring gently. Note that at first blue-white copper (II) hydroxide will form and then redissolve in excess acid. At the end, the precipitate will remain and build up with ensuing drops. This entire process should take about 2 minutes. It should remove all blue color from your solution indicating that all copper has precipitated. Due to the fluffy, gelatinous' nature of the precipitate, it will initially fill most of your solution volume. Note: This gelatinous, flocculent precipitate is typical of most insoluble metal hydroxides. Observe it closely, Give your solution a final stir and let it settle for about I minute. You should be able to see the precipitate settling to the bottom with a colorless clear layer on the top if you look at the beaker from the side. Dip your stirring rod carefully into the clear liquid and check it on litmus paper to 2. Page 7 Experiment 22 A Penny's Worth of Chemistry make sure it is basic. If it is not, consult your instructor-you may have to add more NaOH to get complete precipitation. Note: When all the Cu2t ions have reacted completely with OH ions, the excess hydroxide ions will cause the solution to be basic L. Then, with siring, gently heat the solution just to boiling to convert the copper (Ih) bydroxide to M copper (Il) oxide. Be very careful to heat gradually and stir continuously just until the black C begins to form. You will see the blue-white color precipitate will become much more compact and settle to the bottom. , gradually change to solid black and CAUTION, Alkaline solutions, such as the one you are working with in this step, tend to spatter and bump when they are heated. The boiling chips are added to try to control this by giving vapor bubbles a surface on which to form. Be sure to keep hands and face away from the reaction vessel. 2. Remove from heat and allow your black solid to settle. Have your instructor check your product at this point. After several minutes, carefully decant liquid into another large beaker. Discard decantate directly into drain at end sink and follow with plenty of water to dilute 3. Pour one-third (-150 mL) of the hot water you began heating in step A2 over your black precipitate and stir up the solid for about 15 seconds. Then allow the precipitate to settle and decant the hot water. This process is called a rinse. In this case, the rinse is to remove all traces of acid and nitrate ions from the solid. If they are not removed, they will keep some of the copper metal from forming in the final stage of this lab 4. Repeat the rinse in step C3 above two more times and be sure you keep the rinse water hot. Handle the hot beakers carefully with asbestos gloves or beaker tongs as required. 5. Decant for the final time. Save your black precipitate for part D Part D: Cuo(s) Cu(aq) 1. Add 75 ml. of 6.0M H SO xd your black precipitate from part C and stir to get it to react will get somewhat warm, since the reaction that is occuring is highly completely. It also exothermic, so you will need to handle it carefully You should see the black solid dissolve and a blue color (like the one you had in part A) develop in the liquid. You must make sure all the black solid dissolves. If it does not, consult your instructor 2. 3. Stir your solution and scrape down the sides of your container Decant means to carefully pour off the liquid making sure that none of the solid goes with it. When you decant, you are never able to pour off all the liquid, but you can get most of it. Page 8 Experiment 22 A Penny's Worth of Chemistry Cu(s) Since the next steps generate hydrogen gas in fairly large amounts, CAUTION along with some sulfur oxides, they should be performed in the hood. I. Working in the hood, gradually add about 12.0 g of mossy zinc Jo the blue copper (IID sulfate process and has lots of gas). solution from part. Stir continuously (this is a very ex Now let the reaction run unit the solution becomes mostly colorless as the zinc displaces the copper. You will see bubbling due to the displacement of hydrogen from the sulfuric acid. You will also see a fading of blue color in the solution as rusty red Cu metal forms in the bottom of the beaker. You are through with this part when the solution is colorless. Check with you instructor is you still have significant blue color after 20 minutes. 2. 3. When the displacement of copper is complete, decant the liquid and discard. Be careful to 4. Still in the hood, add 60 mL of concentrate@ HCI yo your solid to destroy the excess zinc metal 5. While you are waiting for step 4 to finish, preweigh a watch glass Also set up a vacuunm 6. When the solution in step 4 stops bubbling, your zine is gone and you are ready to recover your minimize the loss of the copper during you have without affecting the solid copper y after filtration system to recover the copper. Be sure you have a piece of filter paper in your Buchner funnel. copper. Decant all but about 20 mL of your liquid. Turn on the vacuum on your Buchner funnel. Swirl the solution with the solid in the bottom and transfer quickly to the funnel. You goal is to leave as little of the solid behind in the beaker as you possibly can. Put 30 mL of water into the beaker and swirl it, transferring it to the funnel. This process will both remove some of your remaining copper from the beaker and rinse impurities off of the copper. Turn off your vacuum and dump the contents of your filter flask, discarding in the inorganic waste container Measure out 30 mL of acetone in a graduated cylinder and rinse your copper gradually with the acetone. This should remove much of the remaining water. Leave your vacuum filtration running an additional 10 minutes to further dry your filter paper. 7. 8. CAUTION Be absolutely sure there are no more open flames in the lab before measuring out the acetone you will use in the final rinses. This substance is highly flammable. You must keep ACETONE away from open flames 9. Turn off vacuum filtration and carefully transfer all your copper to your pre-weighed watch glass Discard the acetone and methanol in your filter flask into the NOTE. This is the only waste in today's experiment that is organic. (step 5). ic waste 10. Weigh the watchglass containing the copper and determine the mass of copper by difference. 11. Calculate the % Cu in the penny using the mass orcu you recovered Throughout the experiment there are points for observation noted. At these points you are to record the color of the indicated phase which you observed and the chemical formula for the substance being observed. when the observation is of the solution, indicate the ion responsible for the color if there is any. The first line is given as an example: Step Phase Color A3. Solution sły-blue Solid B2. Solution Inev chemial Solid C2. Solution Solid D2. Solution dut Solid

Answer 1

Cbuue) (bourn 3an olue-geen blue buu solid c 2 Си сон), 4→ a.ot ",0 blace The solid black İrcolau γ D2 E2. 23 억 ЕЗ (red) Cbtuu) Due -to -ttre des placerne nt reaction, from blue colourr