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Chemical Reactions

Investigation 3 – Lab

 

 

 

 

 

 

 

MINDSET

Note: The procedural steps are listed below for your reference.

This Investigation is designed to allow you to investigate:

  • how the concentration of a reactant affects the amount of a product,
  • how the consumption of reactant results in the production of a product,
  • the relationship between the amount of reactants and reaction time, and
  • the relationship between the amount of products and reaction time.

BE PREPARED

Student Preparation for the Investigation includes having students gather the following materials. This preparation takes place on lab day after student lab groups have settled at their assigned lab tables.

Note: The materials are listed in students’ SDRs. They are also listed below for your reference.

  • (6) 15 ml centrifuge tubes
  • (1) 50 ml centrifuge tube filled with 40 ml of acetone solution
  • (1) 100 ml beaker filled with 50 ml of water
  • (1) centrifuge tube filled with 15 ml of hydrochloric acid (HCl)
  • (1) centrifuge tube filled with 15 ml of iodine (I2) solution
  • (1) 400 ml waste beaker
  • (4) dropper pipettes
  • (1) test tube rack
  • (1) stopwatch
  • (1) spectrophotometer
  • (1) cuvette
  • (1) box Kim wipes
  • (1) calculator
  • (1) pair goggles per student
  • (1) pair gloves per student
  • masking tape
  • marker pen

Direct one student from each lab group to collect the materials listed in their SDRs.

 

INVESTIGATE

  • You will perform six Trials in this Investigation.
  • Each Trial consists of a separate reaction and each reaction differs in the amount of acetone that is added. The different volume of acetone in the Trials is accounted for by adding different volumes of water. The volumes of iodine and HCl are the same for each Trial.
  • Reflect on the PreLab video as you move through the procedural steps.
  • During the Experiment, every procedural step is important. If one step is skipped, data can become invalid. To help you keep on track, read each step thoroughly, complete the step, then check it off (Read it – Do it – Check it).
  • Remember to wear gloves, safety eyewear, and lab coats when handling chemicals.
  • Complete all of the procedural steps in your SDR.

 

Use the marker and masking tape to label six centrifuge tubes with numbers 1 through 6. Place them in order left to right in the test tube rack.

  1. Refer to Table A for the volumes of the chemicals needed for each tube.

CHEM3 Table A

  1. Use a dropper pipette to add acetone to each tube. Add 1ml of acetone to tube 1, 2 ml of acetone (CH3COCH3) to tube 2, 3 ml of acetone (CH3COCH3) to tube 3, etc. Use the markings on the tubes as a guide.
  2. Use a second dropper pipette to add water to each tube. Add water so that it reaches the 6 ml mark on the centrifuge tube after the proper amount of acetone has already been added. Use the markings on the sides of the tubes as a guide.
  3. Use a third dropper pipette to add 2 ml of hydrochloric acid (HCl) to all tubes 1 through 6. Each centrifuge tube should now reach the 8 ml mark. Use the markings on the sides of the tubes.
  4. DO NOT add iodine (I2) to any tubes.
  5. Replace the caps on all the tubes.
  6. Preparation of the Spectrophotometer: If you need help, read the procedure Spectrophotometer Use and Operation.
    1. Set the wavelength at 460 nanometers using the wavelength control knob.
    2. Blank the spectrophotometer with water. After you have prepared the spectrophotometer, make certain that the mode selection button is set to Absorbance.
  7. Decide which members of the lab group will be responsible for the following tasks.
    1. One group member will add the iodine (I2) solution to each centrifuge tube.
    2. One group member will use the stopwatch to time the reaction.
    3. One group member will record the time in their Student Data Record.
    4. All other group members will observe the spectrophotometer display.
    5. Group members may exchange roles between Trials.

Note: Caution… the iodine solution will temporarily stain skin and permanently stain clothing. you must exercise care to avoid spills. You should especially be careful to screw the caps of the centrifuge tubes tightly before inverting and mixing the reactions.

Trial 1

  1. In this Trial, the reaction in tube 1 will be started by adding the iodine (I2) solution. The procedure must be performed as quickly as possible without spilling the solution.
    1. Using a clean dropper pipette, add 2 ml of the iodine (I2) solution to tube 1. Using the markings on the side of the tube, add iodine (I2) until the volume in the tube is 10 ml.
    2. Quickly screw the cap back on the tube and turn it upside down then upright again. As soon as the centrifuge tube is upside down, start the stopwatch. Turn the tube upside down then upright again 2 more times.
    3. Uncap the tube and pour the solution into the cuvette until it is three quarters (3/4) full. Wipe any liquid and fingerprints on the outside of the cuvette with a Kimwipe.
    4. Place the cuvette in the sample compartment. Push it into the compartment until you hear a click and then close the lid.
  2. Continue to time the reaction and observe the display.
  3. When the display on the spectrophotometer reads .000 or remains unchanged at a reading close to .000, stop the stopwatch.
  4. Record: Write the reaction time in minutes and seconds as it appears on the stopwatch in the row for tube 1 in Table B.
  5. Reset the stopwatch to zero and pour the contents of the cuvette into the 400 ml waste beaker.

Trial 2

  1. In this Trial, the reaction in tube 2 will be started by adding the iodine solution. The procedure must be performed as quickly as possible without spilling the solution.
    1. Using a clean dropper pipette, add 2 ml of the iodine (I2) solution to tube 2. Using the markings on the side of the tube, add iodine (I2) until the volume in the tube is 10 ml.
    2. Quickly screw the cap back on the tube and turn it upside down, then upright again. As soon as the centrifuge tube is upside down, start the stopwatch. Turn the tube upside down then upright again 2 more times.
    3. Uncap the tube and pour the solution into the cuvette until it is three quarters (3/4) full. Wipe any liquid and fingerprints on the outside of the cuvette with a paper towel or wiper.
    4. Place the cuvette in the sample compartment. Push it into the compartment until you hear a click and then close the lid.
  2.  Continue to time the reaction and observe the display.
  3. When the display reads .000 or remains unchanged at a reading close to .000, stop the stopwatch.
  4. Record: Write the reaction time in minutes and seconds as it appears on the stopwatch in the row for tube 2 in Table B.
  5. Reset the stopwatch to zero and pour the contents of the cuvette into the 400 ml waste beaker.

Trial 3

  1. In this Trial, the reaction in tube 3 will be started by adding the iodine (I2) solution. Follow the same steps for this reaction as you used for Trials 1 and 2. Use steps 1 through 3 of Trial 2 as a guide.
  2. Record: Write the reaction time in minutes and seconds for tube 3 in Table B.

Trial 4

  1. In this Trial, the reaction in tube 4 will be started by adding the iodine (I2) solution. Follow the same steps for this reaction as in Trials 1, 2, and 3. Use steps 1 through 3 of Trial 2 as a guide.
  2. Record: Write the reaction time in minutes and seconds for tube 4 in Table B.

Trial 5

  1. In this Trial, the reaction in tube 5 will be started by adding the iodine (I2) solution. Follow the same steps for this reaction as in Trials 1 through 4. Use steps 1 through 3 of Trial 2 as a guide.
  2. Record: Write the reaction time in minutes and seconds for tube 5 in Table B.

Trial 6

  1. In this Trial, the reaction in tube 6 will be started by adding the iodine (I2) solution. Follow the same steps for this reaction as in Trials 1 through 5. Use steps 1 through 3 of Trial 2 as a guide.
  2. Record: Write the reaction time in minutes and seconds for tube 6 in Table B.

 

CLEAN UP

Be sure to clean up your lab bench after finishing your experiment.