Turn on thread page Beta
    • Thread Starter
    Offline

    2
    ReputationRep:
    what colours are

    [Cr(H2O)6]2+

    [Cr(H2O)5(OH)]2+

    [Cr(OH)4]-

    [Co(H2O)4(OH)]+

    [Co(H2O)4(OH)2]

    [Cu(H20)6]2+

    [Cu(H20)4(OH)2]


    Thanks
    Offline

    0
    ReputationRep:
    (Original post by marisad_uk)
    what colours are

    [Cr(H2O)6]2+

    [Cr(H2O)5(OH)]2+

    [Cr(OH)4]-

    [Co(H2O)4(OH)]+

    [Co(H2O)4(OH)2]

    [Cu(H20)6]2+

    [Cu(H20)4(OH)2]


    Thanks

    [Cr(H2O)6]2+ = blue

    [Cr(H2O)5(OH)]2+ = not sure?!

    [Cr(OH)4]- = green

    [Co(H2O)4(OH)]+ = not sure?!

    [Co(H2O)4(OH)2] = blue precipitate

    [Cu(H20)6]2+ = blue

    [Cu(H20)4(OH)2] = pale blue precipitate

    Those are the colours according to my book. It does tend to vary so I would check the mark schemes!!!
    • Thread Starter
    Offline

    2
    ReputationRep:
    marck scheme just sais "know the colours of the compounds in this module" and doesn't actually say the colours, I have the colours in my books of most other compounds but those seem to be missing
    • Thread Starter
    Offline

    2
    ReputationRep:
    Also are [Co(nh3)]2+ and [Co(nh3)6]3+ brown or blue? i have two books with two different colours eek!
    Offline

    1
    ReputationRep:
    (Original post by marisad_uk)
    what colours are

    [Cr(H2O)6]2+

    [Cr(H2O)5(OH)]2+

    [Cr(OH)4]-

    [Co(H2O)4(OH)]+

    [Co(H2O)4(OH)2]

    [Cu(H20)6]2+

    [Cu(H20)4(OH)2]


    Thanks

    Since you're doing AQA, you only need to know the colours of 4 of those complexes.

    Probably been mentioned before but:

    [Cr(OH)4]- = green solution

    [Co(H2O)4(OH)2] = blue precipitate

    [Cu(H20)6]2+ = blue solution

    [Cu(H20)4(OH)2] = blue precipitate



    [Co(NH3)6]2+ = pale yellow (or straw) solution

    [Co(NH3)6]3+ = dark brown solution

    I just go with what the official AQA revision books say.
    Offline

    0
    ReputationRep:
    Hey, on page 252 of the AQA book, it says [Cu(H20)4(OH)2] is pale blue ppt.
    All subsequent mentions are just blue.

    Sorry if this is a stupid question, but I just find it easier to remember pale blue for Copper. They wouldn't let me lose a mark for that, would they?
    Offline

    14
    ReputationRep:
    (Original post by FlamingTelepath)
    Hey, on page 252 of the AQA book, it says [Cu(H20)4(OH)2] is pale blue ppt.
    All subsequent mentions are just blue.

    Sorry if this is a stupid question, but I just find it easier to remember pale blue for Copper. They wouldn't let me lose a mark for that, would they?
    No, far from it you may even need to state that the precipitate is pale blue

    This is because

    [Cu(NH3)4(H20)2]2+ is a deep blue solution

    There for if you add aqueous ammonia dropwise to hexaquacopper (II) ions you'd get a colour change from:

    blue solution --> pale blue precipitate --> deep blue solution
    Offline

    0
    ReputationRep:
    Aha, that does make quite a bit of sense! Cheers for that reassurance.
 
 
 
Turn on thread page Beta
Updated: June 27, 2005
The home of Results and Clearing

3,163

people online now

1,567,000

students helped last year

University open days

  1. Sheffield Hallam University
    City Campus Undergraduate
    Tue, 21 Aug '18
  2. Bournemouth University
    Clearing Open Day Undergraduate
    Wed, 22 Aug '18
  3. University of Buckingham
    Postgraduate Open Evening Postgraduate
    Thu, 23 Aug '18
Poll
How are you feeling about GCSE results day?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.