Chemistry Homework

Lab 9: Chemical Reactions II

Pre-lab Questions

1. Michelangelo used fresco painting when he painted the Sistine Chapel. Fresco painting involves most of the types of chemical reactions you just studied. Listed below are some of the reactions used in creating a Fresco painting. Identify the type of chemical reaction used for each step and balance the chemical equation if needed.

Initially, some sort of heat must be generated. Propane is an example of a common fuel source used for heating.

C3H8 + O2 → CO2 + H2O

This is a ____________________________________________ reaction.

Next, quicklime (calcium oxide) is made by roasting calcium carbonate (limestone).

CaCO3 → CaO + CO2

This is a ____________________________________________ reaction.

The quicklime is slaked to form lime plaster.

CaO + H2O → Ca(OH)2

This is a ____________________________________________reaction.

The lime plaster is cured or dried.

Ca(OH)2 + CO2 → Ca(OH)(HCO3)

This is a ____________________________________________ reaction.

This quickly continues to react to form calcium carbonate and water.

Ca(OH)(HCO3) → CaCO3 + H2O

This is a ____________________________________________ reaction.

Frescos will deteriorate over time when exposed to the damp, acidic environments typical of modern urban city atmospheres.

CaCO3 + H2SO4 → CaSO4 + H2O + CO2

This is a ____________________________________________ reaction.

1. Balance each of the chemical equa_ons you will be doing in this laboratory exercise.

Combustion:

C4H10 (g) + O2 (g) → CO2 (g) + H2O(g)

Synthesis:

Hb (s) + O2 → HbO2 (s)

Single Replacement:

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

Double Replacement:

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

Decomposition:

(NH4)2CO3 (s) → NH3 + H2O + CO2 (g)

Experiment: Getting to Know your Reactions

Procedure

**Take photographs of your experiment set up for Parts 1 - 5 and your results. Submit them with your laboratory report.**

Part 1: Combustion

C4H10 (g) + O2(g) → CO2 (g) + H2O (g)

1. Light a butane lighter and observe the flame. (The ignition of the flame 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 off.

Part 2: Synthesis (A + B → C)

Hb(s) + O2 → HbO2 (s)

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 a>er you exhale.

3. Construct an oxyhemoglobin molecule with modeling clay and toothpicks.

Hint: See figure of molecule in introduction as a guide.

1. Take a photograph of your model and submit it with your laboratory report.

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

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

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.

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

2. 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.

1. 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)

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)

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.

1. Light the candle using the butane lighter.

CAUTION: Long hair should be tied up and loose clothing restrained when around an open flame to prevent fire and burns. Be sure you are wearing your safety goggles.

1. Use a test tube holder to hold the test tube containing the ammonium carbonate at a slight angle in the candle flame. Keep the open end of the tube pointed away from you and other students. Continue to heat the sample until the reaction is finished.

Hint: Remember the products of this reaction are all gases.

1. Record your observations in the Data section.

2. 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 finish cooling.

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

Data

Table 1: Reaction Observations, Parts 1-5

Post-lab Questions

1. Take photographs of your experiment set up for Parts 1-5, including the oxyhemoglobin molecular model from Part 2: Synthesis. Submit them with your laboratory report.

1. Write the combustion reaction that occurs when you cook out on a propane gas grill. Propane has the chemical formula C3H8. Make sure to balance the reaction equation.

1. Balance the following equations and identify the type of reaction.

1. BaCl2 (s) + K2SO4 (aq) → BaSO4 (s) + KCl (aq)

1. KClO3 (s) → KCl (s) + O2(g)

1. H2 (g) + O2 (g) → H2O (l)

1. F2 (g) + LiCl (aq) → LiF (aq) + Cl2 (l)

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