Conversion 1-Changing Cu to Cu(NO3)2: Take Approximately 1

Chemistry Copper Odyssey Lab

Background Information: In this 3-4 day laboratory experiment, you will be make observations of four types of chemical reactions. In Conversion 1, you will be mixing copper and nitric acid to make copper (II) nitrate, nitrogen dioxide and water. In terms of symbols, the chemical change looks like this: Cu(s) + 4HNO3(aq) Cu(NO3)2(aq) + 2NO2(g) + 2H20(l) The brownish-orange gas produced by the reaction is nitrogen dioxide, NO2. The blue color of the solution is that characteristic of many copper compounds dissolved in water. In Conversion 2, you will be adding a basic solution, called sodium hydroxide to neutralize the excess nitric acid. The result will be a pale blue precipitate called copper (II) hydroxide with sodium nitrate as spectator ions. The chemical reaction is as follows: Cu(NO)2 (aq) + 2NaOH(aq) Cu(OH)2(s) + 2NaNO3(aq) In Conversion 3, the conversion of copper (II) hydroxide to black copper (II) oxide in the presence of heat is represented in this way: Cu(OH)2(s) CuO(s) + H20(l) In Conversion 4, the addition of hydrochloric acid (HCl) to copper(II) oxide produces a clear, green solution of copper(II) chloride. CuO(s) + 2HCl(aq) CuCl2(aq) + H20(l) And finally in Conversion 5, this is the reaction that produces the solid copper with which we began: 3CuCl2(aq) + 2Al(s) 3Cu(s) + 2AlCl3(aq) It results in the recovery of metallic copper. Finally, the second step of this chemical change removes any hydrochloric acid that still remains in the beaker: 2Al(s) + 6HCl(aq) 3H2(g) + 2AlCl3(aq)

Purpose: To make qualitative and quantitative observations of four types of chemical reactions – synthesis, decomposition, single replacement and double replacement reactions.

Materials: 1.5 g copper wire or turnings 6 M HNO3 stirring rod 250 mL beaker 6 M NaOH pH paper watch glass or Petri dish 6 M HCl distilled water 1.5 g aluminum funnel bunsen burner w/ clamp 400 mL beaker ice bath ring stand

Procedure: Conversion 1-Changing Cu to Cu(NO3)2: (Day 1) 1. Measure approximately 1.5 g of copper wire or turnings and record the mass in Data-Table 1-1. 2. Place the copper in a 250 mL beaker and carefully add 20 mL of nitric acid (HNO3). 3. Place a watch glass/petri dish on top and make qualitative observations of the reaction that takes place. As soon as you see gas, proceed to step 4. 4. Set the beaker in the fume hood until the copper has completely dissolved.

Conversion 2- Changing Cu(NO3)2 to Cu(OH)2: (Day 2) 1. Test your solution from Conversion 1 with pH paper (the pH expresses the relative acidity of a solution. A pH reading of 7 indicates a neutral solution, a solution that is neither acidic or alkaline. A pH reading of less than 7 indicates acidity; a reading of above 7 shows alkalinity.). Record your result in Data Table 1-2 “Observations prior to change”. 2. Obtain 20 mL of 6 M sodium hydroxide (NaOH) solution and also test it with pH paper. Record your result in Data Table 1-2 “Observations prior to change”. 3. Fill a 400 mL beaker one-third full of ice water. Carefully place the 250 mL beaker containing the solution from Conversion 1 inside the 400 mL beaker so that the beaker floats in water. 4. Add, slowly and cautiously, small portions of the 20 mL sodium hydroxide solution to your copper (II) nitrate solution in the 250 mL beaker. 5. Continuously mix the solution with a gentle swirling motion in the 250 mL beaker. Proceed until all 20 mL of sodium hydroxide solution have been added. The sodium hydroxide, a base, neutralizes, or destroys, the acid properties of the excess nitric acid, still present. You will notice that this neutralization reaction produces considerable heat, so stir well and add the sodium solution slowly. 6. Test the resulting solution with pH paper in Data Table 1-2 “Observations of final product”. If the test paper does not match the original color of the basic sodium hydroxide, add more sodium hydroxide to the 250 mL beaker while mixing until it does. The pale blue precipitate is copper (II) hydroxide.

Conversion 3- Changing Cu(OH)2 to CuO: (Day 2) 1. Add 100 mL of distilled water to the beaker containing the copper (II) hydroxide precipitate. 2. Heat to a gentle boil and stir until all the material is converted to a black-brown substance. This substance is copper(II) oxide. Do NOT let it boil vigorously! 3. Remove the stirring rod from the beaker and let the beaker and the solution cool for 5 minutes. 4. Carefully poor off the extra liquid (don’t lose any solid). 5. Wash the precipitate remaining in the beaker by adding about 75 mL of distilled water and stirring gently. Let the precipitate settle for another 5 minutes and decant (pour off) the wash water, again leaving the solid particles in the beaker.

Conversion 4- Changing CuO to CuCl2: (Day 2) 1. Add 25-30 mL of hydrochloric acid (HCl) to the black copper (II) oxide in the beaker. 2. Stir gently, or cover with a watch glass/petri dish and swirl gently. The oxide will dissolve in a minute or two, leaving a clear, green solution of copper (II) chloride. Wash and decant twice!

Conversion 5-Changing CuCl2 to Cu: (Days 2-4) 1. Add approximately 1.5 g of aluminum to the copper (II) chloride solution. Immediately cover the beaker with a watch glass and allow it to stand. Watch what happens. The aluminum “grows copper hair”. 2. Let the beaker stand overnight. Since the reaction produces hydrogen gas, the absence of bubbles will indicate when the reaction has stopped. (The solution will gradually turn grayish as gas is produced; later you will find that it has cleared when the reaction is completed.) 3. The next class period (Day 3), you will find that the copper has settled. Remove the remaining aluminum wire from the beaker and with forceps remove any small bits of aluminum mixed in with the solid copper. 4. Decant and discard the clear liquid. 5. Wash the copper in the beaker twice with 50 mL portions of hot distilled water, stir, and let settle, decanting the wash water each time. Try not to lose any of the solid copper. 6. Weigh a piece of filter paper to the nearest 0.01 g and record in Data-Table 1-1. Swirl the copper and remaining water in the beaker and quickly pour it into the filter paper. With distilled water wash bottle, gently wash any remaining copper from the beaker into the filter paper. Allow the copper to settle. 7. During the next class period (Day 4), after the filter paper has dried, determine the mass of the remaining copper on the filter paper. Record in Data-Table 1-1. Chemistry Name Period Copper Odyssey Lab

Data: A. Data Table 1-1: Mass of the copper before and after the reactions Original mass of copper Mass of filter paper Mass of paper + copper Final mass of copper

B. Data Table 1-2: Qualitative Observations of each Reaction Observations of materials Observations of reactions Observations of final Reaction prior to reaction and procedures product(s)

1. Cu to Cu(NO3)2

2. Cu(NO3)2 to Cu(OH)2

3. Cu(OH)2 to CuO

4. CuO to CuCl2

5. CuCl2 to Cu

C. Equations: For each of the reactions taking place, include the following: a) word equations b) balanced chemical equation c) brief description of substances Rxn Rxn Type a) Copper (s) + Nitric Acid(aq) Copper (II) nitrate (aq) + Nitrogen Dioxide (g) + water (l)

1 b) Cu (s) + 4 HNO3 (aq) Cu(NO3)2 (aq) + 2 NO2 (g) + 2 H2O(l) c) shiny brown clear colorless bright blue brown clear solid liquid solution gas liquid

D. Calculations: Show your work!

1. Change in mass of copper: Cu (final) – Cu (initial) = ______

2. Percent change in mass: Change in Cu mass x 100= % Cu (initial)

E. Conclusion: 1. a. How do the compounds of copper differ from each other?

b. How do the compounds of copper differ from elemental copper?

c. Give reasons for these differences.

2. Was additional energy needed for any of these reactions? If so, which ones?

3. Did any of the reactions have sufficient energy to proceed on their own? If so, which ones?

F. Error Analysis: 1. Explain in terms of (1) the number of copper atoms, and (2) the law of conservation of mass, why you should or should not have a difference in mass between the initial and final amounts of copper.

2. Determine a minimum of three errors that could account for any gain or loss in copper. BE SPECIFIC and THOUROUGH!