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Chemistry question - help

  1. Jun 24, 2005 #1
    Hello everyone.

    I came here because I'm having trouble with a chemistry question an you guys seem to know what you're talking about =)

    I need to sepearate Ag^+, Ca^2+, and Ni^2+ ions from a solution. each of these is at a 0.1M concentration.

    I've never done this type of question before... what method should I be looking in to?

    I'm thinking maybe I could form precipitates by adding certain anions.. but I'm not sure which ones, I'm also not sure if order matters or when I should be filtering.

    would someone be kind enough to point me in the right direction? :smile:


    thanks
     
  2. jcsd
  3. Jun 24, 2005 #2
  4. Jun 24, 2005 #3
    thanks for the link!




    1) First remove the Ag+ ions by adding HCl(aq) which will precipitate as AgCl(s)

    2) Filter

    3) Remove the Ni^2+ ions by adding H2S(aq) which would form a NiH(s} precipitate.

    4) filter

    5)Remove the Ca^2+ ions by adding (NH_4)_2CO_3 forming a precipitate with ????

    6) filter


    and the ions are removed.


    but what about the fact that I was given .1M concentration for each....am I supposed to have specific amounts that need to be added? or can i just add until the precipitate stops forming?
     
  5. Jun 24, 2005 #4
    altho you are told each metal ion conc = 0.1M, you are not told how much total solution you have to work with. therefore, you can't specify exact reagent amounts to add.

    unless you provide your own "example" metal ion solution amount (say 100 ml), you can only specify to add reagent until precip stops (which will be reagent in slight excess of exact amount required).

    however, if you take an example amount of 100 ml metal ion solution and example reagent solutions of 1M conc, then you can calculate approximate amounts of reagent to add, altho you will still want to add slight excess of reagent.
     
  6. Jun 25, 2005 #5
    thanks for your response =) I think you're right, but at the same time its a little odd that they would give me the concentrations....

    can i get a confirmation from someone? I'm pretty sure that I'm right based on that document you showed me, but just want to make sure.

    thanks
     
  7. Jun 26, 2005 #6
    anyone?

    just want to make sure that i dont have to do anything with the fact that they all have a concentration of .1 M
     
  8. Jun 27, 2005 #7

    siddharth

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    Homework Helper
    Gold Member

    Have you learnt about selective precipitation of salts, and significance of using ksp values? In that method, the concentration of the metal ion is required.

    Also, when you add H2S to Ni2+, the precipitate is NiS (black ppt) and not NiH.
     
  9. Jun 27, 2005 #8
    thanks for the response, yes I did learn about Ksp values, and their significance, but its been awhile :smile: I'll look into that now.

    also,

    Remove the Ca^2+ ions by adding (NH_4)_2CO_3

    any idea what precipitate this would form?
     
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