Chem+1+Unit+2+Lab



=**Chemistry Unit 2 Lab: Copper Cycle**= Chemical reactions are often accompanied by formation of a precipitate, evolution of gas, change in color, or pronounced temperature change. In this activity, you will observe these characteristics of chemical reactions.
 * Introduction**

To recognize that change of state, change in color, formation of a precipitate, or the evolution of heat are associated with a chemical change; to study reactions of copper.
 * Purpose**

Wear protective goggles and an apron or lab coat at all times. Avoid skin contact with solids and solutions. Dispose of all solutions in the waste containers provided. Wash your hands before leaving the laboratory.
 * Safety Considerations**

1.Obtain a copper turning and record the mass in your data table. 2.Bring your copper turning to Ms. Lee in the fume hood to apply Nitric acid, HNO3. This must be done in the fume hood. (Caution: Avoid breathing poisonous gases. Avoid contact of skin with nitric acid. It burns skin and clothing.) The products formed are copper(II) nitrate solution, Cu(NO3)2(aq), and nitrogen dioxide gas, NO2(g). 3.Use a small graduated pipet to add 2.0 ml sodium hydroxide solution, NaOH(aq). (Caution: Avoid contact with sodium hydroxide.; it burns skin.) Add this slowly to the test tube. This reaction may give off heat. (In other words, it may be exothermic.) 4.Tap the tube firmly to mix or use a stirring rod. 5.Add about 1/3 of a pipet of distilled water. Tap or stir to mix. The solid material is copper(II) hydroxide, Cu(OH)2(s). 6.Place your test tube in a hot water bath. Remove the test tube when you see no further change occurring. This product is copper(II) oxide, CuO(s). Run cold water over the outside of the test tube to cool it. 7.Allow the material to settle or use a centrifuge to spin the solution. Decant or use the pipet labeled "waste" to remove the clear liquid (supernatant liquid) above the copper(II) oxide. Do not remove any of the solid. 8.Discard the liquid and wash precipitate by adding about half a pipet of distilled water. Tap or stir to mix. 9.Allow the solid to settle. Then remove and discard the liquid, or centrifuge and decant.
 * Procedure**
 * 1) To the precipitate, add 3.0 ml hydrochloric acid, HCl, using a small graduated pipet. (Caution: Avoid contact of both skin and clothing with hydrochloric acid.) Tap or stir to mix. This new product is copper(II) chloride solution, CuCl2(aq).
 * 2) Add the precut piece of aluminum wire to the test tube. (The wire should be bent like a fish hook to hook over the top of the test tube.) Place the test tube in a cold water bath. This reaction is very fast! (Instead, your teacher may tell you to run cold water over the outside of the test tube. Be sure to use a test tube holder to hold the test tube since the reaction gives off considerable heat.) The products forming in this step are hydrogen gas, H2(g), aluminum chloride solution, AlCl3(aq), and metallic copper, Cu(s).
 * 3) When the reaction is finished, remove and discard the liquid.
 * 4) Wash the solid with half a pipet of distilled water. Discard the liquid.
 * 5) Wash the solid again with half a pipet of fresh distilled water, and filter.
 * 6) Use tweezers to remove any leftover pieces of aluminum wire. Observe the final product.
 * 7) Take the filter paper with your product and mass your copper when dry.
 * 8) Clean pipets, test tube, and funnel.
 * 9) Wash hands thoroughly before leaving the laboratory.


 * Data**
 * Initial Mass of Copper ||  ||
 * Final Mass of Copper ||  ||

Use your observations to complete your data table below. Be sure to include the observations that alerted you that some type of chemical change was occurring.

Al + HCl à AlCl3 + H2 ||  ||
 * ** Reaction ** ||  ** Observations **  ||
 * Cu + 4HNO3 à Cu(NO3)2 + 2NO2 + 2H2O ||  ||
 * Cu(NO3)2 + 2NaOH à Cu(OH)2 + 2NaNO3 ||  ||
 * Cu(OH)2 + Na2SO4 à CuO + H2O + Na2SO4 ||  ||
 * CuO + 2HCl à CuCl2 + H2O ||  ||
 * CuCl2 + Al à Cu + AlCl3


 * Post-lab Questions and Calculations**
 * 1) What is the difference between the initial mass of copper and the final mass of copper.
 * 2) What is the error and percent error in your experimental data?
 * 3) How do your findings relate to the Law of Conservation of Mass?