Lab 11: Photochemistry

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For this lab, we are going to perform the photochemical reaction of iodine and oxalate. We will be running the experiment until two hours after we set it up, so we will likely go 15 or so minutes over our usual lab time.

We will also do other labs and activities as demonstrations to fill in while we wait between observations of the experiment. You won’t be asked to write those up in your lab notebook.

Reading:  The Home Scientist Lab Manual Topic XI. Photochemistry Session XI-1: Photochemical Reaction of Iodine and Oxalate pp. 182-186. This will be the lab we are writing up. 

Two demonstrations we will be doing from the Home Scientist:  Topic III Session 1 and 2, read pp. 70-74. You do not need to write these up.

Experimental Title: Lab 11:  Photochemical Reaction of Iodine and Oxalate

Date of laboratory:  August 12, 2014

Purpose: The purpose of this laboratory is to observe photochemical initiation of the oxidation of iodine to iodide by oxalate, as well as to determine the effect of wavelength on photochemical initiation of a reaction.


Read the background to the experiment on page 183-top 0f page 184.

Write the equations for the reactions in your notebooks. Also, summarize what the color changes or lack of color changes mean about how far the reaction has progressed.

Special safety concerns for Lab 11:

  • This week the most hazardous material is the 6M Ammonia.Please use gloves and goggles at all times when handling this material. It is corrosive and the vapor can be irritating. (MSDS for 6M Ammonia)
  • You may remember from the oscillating reaction that iodine can stain. Sodium thiosulfate makes it colorless again.
  • If glass test tube breaks, do not pick it up with your bare hands. Notify your instructor immediately.
  • Be sure to wash your hands very carefully when you are finished with this lab.

Materials:  See list page 183.


(Public domain image by George Hodan)



Write down the Procedure on pages 184-186 the lab manual. Be sure to leave room for the data table to record your results.


Once you have completed the experiment and cleaned up, sit down and write a sentence or two to explain the results. It is always a good idea to do this part while the experiment is fresh in your mind.


Record any thoughts you have about the experiments, including:

  • Possible improvements to the procedures or how to tweak techniques
  • How the results differed from your expectations
  • Whether the goals were met
  • Suggestions for other experiments
  • The answers to the review questions he provides on page 186.

Please leave a comment or send an e-mail if you have any questions before our meeting.

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