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    Kw of water at 10 degrees is 3x10-^15 mol 2 Dom-6 and at 50 degrees it is 5.50 x 10-^14 mol dm-6. Calculate pH of water at both temps and state if it's acid, alkali or neutral.
    For 10 degrees I got 14.5
    For 50 I got 13.3
    Don't think it's right. Can someone explain how to do this question and what the right answer is? Thank you
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    Sorry you've not had any responses about this. Are you sure you’ve posted in the right place? Posting in the specific Study Help forum should help get responses.

    I'm going to quote in Tank Girl now so she can move your thread to the right place if it's needed. :yy:

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    (Original post by AqsaMx)
    Kw of water at 10 degrees is 3x10-^15 mol 2 Dom-6 and at 50 degrees it is 5.50 x 10-^14 mol dm-6. Calculate pH of water at both temps and state if it's acid, alkali or neutral.
    For 10 degrees I got 14.5
    For 50 I got 13.3
    Don't think it's right. Can someone explain how to do this question and what the right answer is? Thank you
    10 degrees: (3 x 10-15/1.0x 10-7)= 3 x 10-8
    50 degrees: (5.50x 10-14/ 1.0 x 10-7) = 5.5x 10-7

    -Log [H+] = pH

    10 degrees: 7.52 therefore neutral
    50 degrees: 6.25 therefore acidic
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    (Original post by AngryRedhead)
    10 degrees: (3 x 10-15/1.0x 10-7)= 3 x 10-8
    50 degrees: (5.50x 10-14/ 1.0 x 10-7) = 5.5x 10-7

    -Log [H+] = pH

    10 degrees: 7.52 therefore neutral
    50 degrees: 6.25 therefore acidic
    Thanks so much!!

    Why did u divide it by 1.0x10--7 thoo??
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    (Original post by AqsaMx)
    Thanks so much!!

    Why did u divide it by 1.0x10--7 thoo??
    Because Kw is [H+][OH] So half of 1.0 x 10-14 is 1.0 x 10-7. Btw I gave you the wrong determination above, they are both neutral tions as in pure water the conc of H+ and OH- is always equal
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    (Original post by AngryRedhead)
    Because Kw is [H+][OH] So half of 1.0 x 10-14 is 1.0 x 10-7. Btw I gave you the wrong determination above, they are both neutral tions as in pure water the conc of H+ and OH- is always equal
    I don't get how they're both neutral?

    I got 7.3 for 10
    And 6.6 for 50
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    (Original post by AqsaMx)
    I don't get how they're both neutral?

    I got 7.3 for 10
    And 6.6 for 50
    Because if the concentration of [H+] and [OH-] is equal they cancel out. Remember that this is pure water we are talking about.

    Some variation is expected depending on your calculator model; examination mark schemes usually have an accepted range on it to account for this. Your answers look alright to me.
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    10 DEGREES I got pH= 7.26 ( ALWAYS TO 2.D.P CHEM OCR A )
    50 DEGREES i got pH= 6.63

    kW= [ H+]2
 
 
 
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