Lab 8 Chemical Reactions

Introduction There are millions of chemical reactions occurring around us during every second of every day. Chemical reactions are involved in the making of food, paper, plastics, pharmaceuticals, fuel, soaps, and numerous other products that we enjoy using. They also enable us to breathe, grow, see, and digest and metabolize food for energy. In this laboratory activity, you will perform five reactions, look for evidence of a chemical reaction, write the chemical equations, and classify the reactions according to reaction types.

Materials & Equipment 0.5 M calcium chloride solution, 3-4 mL 0.5 M silver nitrate solution, 5 mL copper wire, 4 inches long copper carbonate magnesium metal ribbon, 5 cm long 0.50 M sodium carbonate solution, 3-4 mL

scoop or spatula wooden splint pipets, 3 test tube clamp Bunsen burner and matches test tube rack and test tubes crucible tongs watch glass

Safety Precautions Copper carbonate is a body tissue irritant. Silver nitrate will readily stain skin and clothing brown and is mildly toxic by ingestion. Avoid contact with all chemicals. Wear chemical splash goggles. You may wear gloves and an apron during reaction #4 if you choose.

Procedure Before beginning each reaction, record qualitative observations of the reactant(s) in your data table. Following completion of each part, record similar qualitative observations of the product(s).

Reaction #1 Caution: Copper(II) carbonate is a skin irritant.

1. Place a scoop of copper(II) carbonate (CuCO3) in a clean, dry test tube. Note and record the appearance of the sample. Light your Bunsen burner.

2. Using a test tube clamp, heat the CuCO3 strongly for about three minutes. Remove the test tube from the heat source and rest it in your test tube rack or a beaker.

3. Light a wood splint and then insert the burning wood splint into the test tube. If carbon dioxide gas (CO2) is present, it will put the flame out. Record the results of this test. Note and record any change in the appearance of the product in the test tube.

Reaction #2

4. Obtain a strip of magnesium metal ribbon about 5 cm in length. Record your observations of the magnesium before burning it. Light your laboratory burner. 5. Hold the piece of magnesium metal ribbon with a pair of tongs. Place the ribbon in the burner flame and allow it to burn. As the magnesium ribbon burns, hold it over a watch glass and allow the remains to drop into the watch glass. DO NOT LOOK DIRECTLY AT THE BURNING MAGNESIUM. The bright light emitted by the burning magnesium ribbon is UV light which can damage your eyes. Observe by looking slightly to one side and using peripheral vision. Extinguish your burner at this point. You will not use it again in this lab.

6. Record your observations of the product.

Reaction #3

7. Place a test tube in a test tube rack. Add 2 droppers-full of a 0.5 M CaCl2 solution.

8. Add 2 droppers-full of a 0.5 M Na2CO3 solution to the test tube. Record your observations.

Reaction #4 Caution: silver nitrate can stain skin and clothing.

9. Place a test tube in a test tube rack. Fill the test tube about one-third-full with 0.5 M AgNO3 solution.

10. Obtain a piece of copper wire about 4 inches in length. Wrap the wire about a pencil so that it forms a coil. Record your observations of the reactants before mixing.

11. Submerge the coiled copper wire into the silver nitrate solution. Observe for several minutes as the wire reacts with the solution. Allow the contents of the test tube to rest in the test tube rack for as much time as you have. Record your observations of the new solid and solution after the reaction is complete.

Reaction #5

12. The Bunsen burners we use in the lab contain methane (CH4). The methane combines with oxygen in the air and the reaction releases energy in the form of heat and light. Record information for this equation in your data table.

Cleanup and Disposal

All solids must go in the trash can, not the sink. This includes the product in the test tube from reaction #1, unreacted Mg and the product of reaction #2 and unreacted Cu wire from reaction #4. The precipitate and solution from reaction #3 may be flushed down the sink. Rinse out your test tubes and watch glass.

Analysis After completion of all reactions write a balanced chemical equation for each. For reaction #1, determine your solid product based upon the following information. Copper(I) oxide is a red powder; copper(II) oxide is a black powder. For reaction #4, the blue solution formed is copper(II) nitrate. Name Date Period

Reaction #1

Observations

Evidence That a Chemical Reaction Occurred

Balanced Chemical Equation

Type of Reaction

Reaction #2

Observations

Type of Reaction

Reaction #3

Observations

Type of Reaction

Reaction #4

Observations

Type of Reaction

Reaction #5

Observations

Type of Reaction

Conclusions

Do any of the reactions performed in this laboratory activity fall into more than one category of reaction type? If so, which ones? Cite evidence supporting your claims.