Lab: Chemical Reactions

Procedure

Part 1: Combustion

C₄H₁₀ (g)   +  O₂(g)   →     CO₂ (g)   +  H₂O (g)                             unbalanced

1. Light a butane lighter and observe the ?ame. (The ignition of the ?ame is a reaction between butane and the oxygen in the air you breathe.)

2. Record your observations in the data table from when the lighter is turned on until it is turned o?.

Part 2: Synthesis (A + B → C)

Hb(s)              +       O₂         →         HbO₂ (s)                                                unbalanced

1. Take a deep breath, hold it as long as possible and then exhale. Visualize the reaction occurring.

2. Record your observations before inhaling and after you exhale.

3. Construct an oxyhemoglobin molecule with modeling clay and toothpicks. HINT: See ?gure of molecule in introduction as a guide.

Part 3: Single Replacement (A + BC → AC + B)

Zn (s)  +  H₃C₆H₅O₇ (aq)  →                    Zn₃(C₆H₅O₇)₂ (aq)               + H₂ (g)                   unbalanced

1. Place a test tube in a test tube rack or small beaker.

2. Slightly tilt a test tube and slide a small zinc-coated (galvanized) washer down the side.

3. Use a 10 mL graduated cylinder to measure out approximately 2 mL of saturated citric acid and carefully pour it into the test tube containing the zinc washer. CAUTION: Citric acid is irritating to the eyes and skin.

4. Observe the reaction for several minutes, and record your observations in the data table.

5. To clean up, separate the acid solution from the washer by pouring it into a small beaker while leaving the washer in the test tube. This is called decanting. Rinse the test tube containing the washer several times with water and add each rinse to the beaker- CAUTION: Do not pour the acid directly down the drain. To neutralize the acid, add small amounts of baking soda to the solution in the beaker and stir with a stirring rod.

6. Continue stirring and adding small amounts of baking soda until gas no longer forms. Pour the liquid down the drain and throw the washer in the trash.

Part 4: Double Replacement (AB + CD → CB + AD)

Zn(C₂H₃O₂)₂ (aq) +Na₃PO₄ (aq)→ NaC₂H₃O₂ (aq) + Zn₃(PO₄)₂ (s)                                              unbalanced

1. Pour approximately 2 mL of 0.1 M zinc acetate (Zn(C₂H₃O₂)₂) into a clean test tube.

2. Add approximately 2 mL of 0.1 M sodium phosphate tribasic (Na₃PO₄) into the test tube.

3. Record your observations before and after the addition of Na₃PO₄ in the data table.

4. To clean up, pour the contents of the test tube down the drain.

Part 5: Decomposition (AB → A + B)

NH₄)₂CO₃ (s)   →                    NH₃           +       H₂O         +  CO₂ (g)                  unbalanced

1. Place a spatula tip full (approximately 0.02 g) of ammonium carbonate (NH₄)₂CO₃, powder into a test tube. CAUTION: Do not inhale the strong ammonia odor. Try to work in well ventilated area.

2. Light the candle using the butane lighter. CAUTION: Long hair should be tied up and loose clothing restrained when around an open ?ame to prevent ?re and burns. Be sure you are wearing your safety goggles.

3. Use a test tube holder to hold the test tube containing the ammonium carbonate at a slight angle in the candle ?ame. Keep the open end of the tube pointed away from you and other students. Continue to heat the sample until the reaction is ?nished. Hint: Remember the products of this reaction are all gases.

4. Record your observations in the Data section.

5. Allow the test tube to cool to room temperature before touching it. CAUTION: The test tube will be very hot and can burn your skin if touched before it cools. Hint: After the test tube has cooled for a few seconds, place it in a small beaker or test tube rack to ?nish cooling.

6. Extinguish the candle. Wash out the test tube with soap and water.