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Homework Help: Can someone check this for me please?

  1. Aug 26, 2007 #1
    Can someone check this for me please??

    The solubility of silver sulphate is 1.3 x 10^-6 mol/L at 20 degrees celcius.

    a) write the equation for the dissolving of this salt in water.
    b) show the Ksp expression.
    c) calculate the value of the Ksp at 20 degrees celcius.


    a) 2Ag+(aq) + SO4 2-(aq) = Ag2(SO4)

    b) Ksp = [Ag+]^2[SO4^2-]

    c) I am having trouble withthis: Ksp= (1.3 x 10^-6)(1.3 x 10^-6) = 1.7 x 10^-12
  2. jcsd
  3. Aug 26, 2007 #2
    lol wrong place. let me work it out.
  4. Aug 26, 2007 #3
    lol thanks...and I'm a girl! :)
  5. Aug 26, 2007 #4
    lol i thought about that when i said bro, so i edited my comment but you checked it fasttt! haha

    anyways, so i'm assuming C is your work?

    [tex]Ag_2SO_4 (s) \rightarrow 2Ag^{+} (aq) + SO_4^{2-} (aq)[/tex]

    You're given [tex]K_{sp}=1.3x10^{-6} M[/tex] of Silver Sulfate, and so when you write your [tex]K_{sp}[/tex] equation it will look like this. (You have it correct, I'm just blabbering)

    [tex]K_{sp}=[Ag^{+}]^2[SO_4^{2-}][/tex] and [tex]Ag_2SO_4 (s)[/tex] is not included b/c we don't include liquids/solids since their concentration change is negligible.

    Let [tex]x=1.3x10^{-6}, x=[2S]^2[/tex]

    simplifying and skipping steps



    and that's all.
    Last edited: Aug 26, 2007
  6. Aug 26, 2007 #5
    Ok. Well first, I have this one question I have posted before. I really have no clue what they are asking me, I do not know what to do or where to start. Maybe if you have any ideas I can work with it...

    A solution contains the following ions, each at a 0.1 M concentration.

    Ag+ (aq), Ca2+ (aq), Ni2+ (aq)

    write out a procedure by which these ions may be separated from each other and from the solution, clearly indicating the order of separation and when filtering should be done.

    So, what is this procedure and order of separation they are talking about? I have no clue what is going on here.
  7. Aug 26, 2007 #6
    i'm not very good at these type of questions (i didn't care for labs too much, i'm lazy), but what comes to mind is solubility rules & activity series of metals.

    i'm sure someone will respond :-]
  8. Aug 26, 2007 #7
    OK, and I am having the same kind of issues with this one:

    An electrochemical cell is constructed by placing a nickel electrode into a 1.0 M NiSO4 solution, and a silver electrode into a 1.0 M AgNO3 solution, and then joinging them with a salt bridge to complete the circuit.

    a) give the anode half reaction and the E0 value.
    b) give the cathode half reaction and the E0 value
    c) give the net reaction and its E0 value
  9. Aug 26, 2007 #8
    i think i have an idea

    [tex]Cl^{-}[/tex] is soluble except in the presence of [tex]Ag^{+}[/tex] in which it is a solid.

    so add [tex]Cl^{-}[/tex] to react with Ag, so now you've taken care of Ag -> AgCl (s)
  10. Aug 26, 2007 #9
    read this thread real fast https://www.physicsforums.com/showthread.php?t=181411

    and i will work on your problems while thinking of some questions to ask
  11. Aug 26, 2007 #10
    ok i got it worked out, my question is. what is the purpose of Sulfate and Nitrate?

    what are the charges for the individual ions? Ni, SO4, Ag, NO3?
  12. Aug 26, 2007 #11
    The common charges?

    Ni2+, Ag1+, SO4 2-, NO3 1-....right?
  13. Aug 26, 2007 #12
    EDIT: lol ... you have it right, idk what i'm thinking, anyways moving on

    so did you read the other thread?

    so now look at the reduction potential table and tell me which one you would choose to be your cathode and anode?
    Last edited: Aug 26, 2007
  14. Aug 26, 2007 #13
    lol btw the four of them?
  15. Aug 26, 2007 #14
    or just between NiSO4 and AgNO3
  16. Aug 26, 2007 #15
    I would have to say AgNO3 cathode...
  17. Aug 26, 2007 #16
    you didn't answer my question, what is the purpose of Nitrate and Sulfate?

    look at your reduction potential table, are you able to find them?

    why do you choose AgNO3 as your cathode?
  18. Aug 26, 2007 #17
    I am so confused
  19. Aug 26, 2007 #18
    sigh :-[ ok let's move on

    a rule of thumb, [tex]E_{cell}>0[/tex], we need to choose which one will be the cathode/anode so that [tex]E_{cell}[/tex] is positive.

    tell me the what the half-reactions for [tex]Ag^{+}[/tex] and [tex]Ni^{2+}[/tex].
  20. Aug 26, 2007 #19
    Okay, like so?

    Ag -> 2g-
    is that right for Ag+
  21. Aug 26, 2007 #20
    Ag-> Ag+ + e- is oxidation right?
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