1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Cobalt Colours

  1. Mar 12, 2013 #1
    I have heard, quite simplistically, that "CoCl2 goes blue to pink with water" and "the reverse occurs with HCl solution". I have also heard that Co, and CoCl2, are pink in solution with water (in both cases with a different complex ion formed), and in both cases adding HCl again turns the solution blue.

    So there are three cases: solid CoCl2, CoCl2 solution, and plain Co in solution. In each case I will need to know which complex ions are responsible for each colour produced.

    The Internet has helped but I can't find out more from it than I already have, which is that Co2+ immediately forms [Co(H2O)6]2+ in solution, which is responsible for the pink colour, and that adding Cl- ions (e.g. HCl solution) then converts this to the blue [CoCl4]2- ion. So the plain Co in solution case is solved.

    But what happens in the other two cases?
    Last edited: Mar 12, 2013
  2. jcsd
  3. Mar 24, 2013 #2
    with Co being a metal, are you sure that it is soluble in water?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted