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Homework Help: Calculating pH from pKw

  1. Apr 10, 2016 #1
    1. The problem statement, all variables and given/known data
    pKw for water at 10 deg Celsius is 14.54. What is the pH of pure water at this temperature?

    2. Relevant equations
    kHw = [H+][OH-]

    3. The attempt at a solution
    I don't even know where to start on this one
  2. jcsd
  3. Apr 10, 2016 #2
    one can start with definitions like pKw ,pH etc go to the text books or Google it
  4. Apr 10, 2016 #3


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    Gold Member

    You could write the equation for the dissociation of water, and then ask what would be the relation between [H+] and [OH-].
    And anyway what about electroneutrality?

    It would be best to work this out yourself, perhaps the above will remind you of stuff you already studied. If not, go back to probably about the first section about pH in your textbook.
  5. Apr 11, 2016 #4
    [H+]^2 = 10^-14.54
  6. Apr 11, 2016 #5
    perhaps you have taken H and OH ion concentration equal-why so?

    The acid potential of aqueous solutions is measured in terms of the pH scale.
    The symbol "p" means take the negative logarithm of whatever follows in the formula. for pH, pOH, p[anything] .

    The pH scale is a logarithmic scale.
    Every multiple of ten in H ion concentration equals one unit on the logarithm scale.
    Physically the pH is intended to tell what the acid "potential" is for a solution.

    In a sense the system is INVERTED so a low pH value indicates a great acid potential
    while a high pH indicates a low acid potential. ( Sad but true this is upside down and counter intuitive.)
    The pH values range from negative values to number above 14. Commonly the scale is often misrepresented as ranging from 0 to 14. We will find that negative values are possible.
  7. Apr 11, 2016 #6


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    Looks OK to me.
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