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Can you anyone help me to set up a ice chart for this one?

  1. Dec 18, 2009 #1
    1. The problem statement, all variables and given/known data

    if the pH is 9.72 for the following 2 bases. what is the initial conc. of the bases
    a)LiOH
    b)HCN
    the answer for a is 10^-4.28, but i don't know how to set up an ice chart

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Dec 18, 2009 #2

    chemisttree

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    Science Advisor
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    Gold Member

    For a), you don't need an ICE chart. You need pH=-log[H+] and [H+][OH-] = 10-14
     
  4. Dec 18, 2009 #3
    Yes, but I still want to know what the ice chart like,
    and for b, can you help me to set the ice chart, cuz HCN is weird
    H3O+ + CN- <--> H2O + HCN
    is this right ?
    thanks!
     
  5. Dec 20, 2009 #4

    Borek

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    Staff: Mentor

    CN- + H2O <-> HCN + OH-

    Nothing weird, this is Brønsted-Lowry base.

    Note: in the case of bases you have to calculate concentration of OH-, then to convert it to pH.

    ICE tables are built exactly the same way as for acids, just OH- is the product (concentration of water in the case of cyanide is assumed to be not changing and ignored). You will be not able to solve LiOH with ICE table, as LiOH is considered to be a strong base, 100% dissociated, so final concentration of LiOH will be 0 - and you can't divide by zero.

    --
     
  6. Dec 20, 2009 #5
    but,when i wrote out the the species
    HCN(aq)
    SA_____A
    H30+ , H2O , CN-
    _______B___ SB
    Isn't the SA react with SB?
    H3O+ + CN-?
     
  7. Dec 20, 2009 #6

    Borek

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    I am not familiar with this notation, please elaborate.

    These would react IF there would be enough H+ (H3O+). Concentration of water is much much larger, especially if you start with neutral solution.

    --
    methods
     
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