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Destroyer Gchem question

Discussion in 'DAT Discussions' started by yankees27th, Dec 24, 2008.

  1. yankees27th

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    #140:
    The Kw for at the given temperature is 5x10^-14. How does this make the water more acidic? I understand that there's more H+, but there's more OH- too. How do you know it's not slightly basic?
     
  2. doc3232

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    pH is based on concentration of H+ ions and nothing else. It doesn't matter if there is 1000 molar OH- in the solution.
    Hence, a lot of H+ and a lot of OH- is read only as a lot of H+. Aka acidic.
     
  3. yankees27th

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    But if you find the pOH and then subtract that from 14 don't you get that it's basic?
     
  4. doc3232

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    I think the 14 only applies at room temp.
     
  5. doc toothache

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  6. zuma35

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    Actually, the water is neither acidic nor basic. It's neutral. [H+][OH-]=Kw. The pH ithe negative log of the [H+]. Thus, at Kw=1*10^-14, the H+ OH- concentrations would both be 1*10^-7, and the pH and pOH would be 7. In our case, the Kw is 5*10^-14 and thus the [H+] and [OH-] would each be 2.2*10^-7, making the pH and the pOH both 6.65.

    Remember, acidic means that there is more H+ than OH-. If they are equivalent, it is neutral no matter what the pH is. pH=7 is neutral only when Kw=1*10-14.
     
  7. doc3232

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    Is that the official definition of acidic? If so, then I don't know what to say.
     
  8. zuma35

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    Yes. An acidic solution means there is more H+ than OH-. Check your general chem book if you're unsure.
     
  9. Panther85

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    dont forget that "acid" has 3 definitions... Arrenheus, Bronsted-Lowry, and Lewis. so make sure that u know the differences
     
  10. Sublimation

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    Thats correct, just be able to differentiate between them.
     
  11. sciencegod

    sciencegod Super Member
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    correct. three defifntions. one is with the H and OH. the othr is with the dots moving. and the other one also is with the H and OH.
     
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