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Homework Help: Chem problem

  1. Jun 8, 2005 #1


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    hi forum,
    would nebody be able to help me solve this problem?

    0.18mol of potassium cyanide (KCN) was dissolved in 1.00L of a solution in which the pH was held constant at 9.70 at a temperature of 298K.

    the equilibrium concentration of CN- was 0.13M.

    Calculate Ka for the weak acid HCN.

    ne help would be greatly appreciated. :)
  2. jcsd
  3. Jun 8, 2005 #2
    What kind of an electrolyte is KCN? What do you think will happen when KCN is put in a solution the pH of which is "held constant"? What are the ions in solution? What are the constraints?

    How about showing us what your reasoning/working is so far, first?
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