Cobalt chloride le chateliers principle

Discussion in 'Supporting Chemistry' started by Kyle Vincent, May 16, 2018.

  1. Hi all

    Tomorrow I plan to show my students this demo (rsc instructions). Up until now I've mainly taught science up to IGCSE only so have less experience setting up practicals for key stage 5. I'm a teacher and technician!

    Just wondered if anyone had any safety tips or other advice for this practical. My conc HCl is at 32% and I'm not used to using conc HCl in front of students, what would be the best method of transferring it to measuring cylinder etc?

    Also understand CoCl2 should be handled in a fume cupboard (switched off) until in solution - this isn't a chemical I've worked with before.

    Once equilibrium set up (violet colour) we'll be adding HCl and H2O to observe colour Changes and also altering the temperature using water baths to observe the shift in equilibrium position.

    Thanks for any advice.
  2. I would do everything up to the instruction: "If necessary, add more hydrochloric acid or water by trial and error to produce an ‘in-between’ violet-coloured solution containing a mixture of the two cobalt ions. Place about 2 cm depth of it in each of the six boiling tubes in two groups of three in suitable racks." behind the scenes first.
    Then you should only need to take the 6 tubes and a small amount of HCl into the lesson (which could be in a sealed vial or bottle until you need to add it. I wouldn't take a measuring cylinder of it in- sounds easy to spill).
  3. 007


    I use a fume cupboard for this and conc HCl of 38%. It works really well. I have some stored in sealed boiling tubes which makes showing the temperature change really easy.

    I also do another equilibrium of the following: upload_2018-5-16_8-33-59.png
  4. I have been asked for reversible reactions before, but haven't done anything like this. Given that once prepared, can be sealed and reused, will point it out to my friendly chemist (and chaperone with conc stuff). Was about to ask if can be kept.. CLEAPSS suggests it keeps 1 year or more...
    (oops- I am referring to the cobalt chloride reaction above...)
    Last edited: May 16, 2018
  5. Thanks for all the help guys. Might have a look at the Fe3+ equilibrium another year, don't have the chemicals needed at the moment!
  6. Success!

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