AP Chemistry

A given weak acid HZ has a Ka=1.7×10−6.
What is the H3O+ concentration of a solution of HZ that has a concentration of 0.78 mol/L?
What is the pH of this solution of HZ?
What is the percent ionization of HZ in this solution?
Answer in units of %

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  1. I am sure if a chemistry teacher comes by you will be helped. I am a physicist and can only answer really easy chemistry questions, sorry.

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    posted by Damon
  2. I can not help with this.

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    posted by Damon
  3. ........HZ + H2O ==> H3O^+ + Z^-
    I......0.78M.........0........0
    C........-x..........x........x
    E.....0.78-x.........x........x

    Ka = (H3O^+)(Z^-)/(HZ)
    Use Ka, plug in E line of ionization above and solve for x = (H3O^+).
    Then pH = -log(H^3O^+)
    %ion = [(H3O^+)/0.78]*100 = ?
    Post your work if you get stuck.

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  4. I got the first two parts correct but I can't seem to get the last part. The concentration I got for H3O^+ is 1.151520734e-3. When I plugged that in for the %ion I got 0.1476308633. I typed that into my homework and it said that is incorrect.

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  5. I have the same answer you obtained BUT my best guess is that you have reported too many significant figures. You are allowed only two; therefore, I would round that off to 0.15%. Let me know if that clears up the problem (or doesn't clear up the problem).

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  6. I tried .15 and it said it was incorrect.

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