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lnk = lnA - Ea / RT question Watch

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    Please can someone check if this is right?

    k = 6.51 x 10^-3 mol-1dm3
    T = 300K
    A = 2.57 x 10^10 mol-1dm3
    R = 8.31 JK-1mol-1

    Using lnk = lnA - Ea / RT find Ea in kJmol-1


    I did:

    ln6.51 x 10^-3 = ln2.57 x 10^10 - Ea / 8.31 x 300
    -12550.79... = ln2.57 x 10^10 - Ea
    Ea = ln2.57 x 10^10 + 12550.79...
    Ea = 12574.768... Jmol-1
    Ea = 12.6 kJmol-1 (3.s.f)
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    Anyone?
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    (Original post by kiiten)
    Please can someone check if this is right?

    k = 6.51 x 10^-3 mol-1dm3
    T = 300K
    A = 2.57 x 10^10 mol-1dm3
    R = 8.31 JK-1mol-1

    Using lnk = lnA - Ea / RT find Ea in kJmol-1


    I did:

    ln6.51 x 10^-3 = ln2.57 x 10^10 - Ea / 8.31 x 300
    -12550.79... = ln2.57 x 10^10 - Ea
    Ea = ln2.57 x 10^10 + 12550.79...
    Ea = 12574.768... Jmol-1
    Ea = 12.6 kJmol-1 (3.s.f)
    I make it 72.3 kJ
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    (Original post by charco)
    I make it 72.3 kJ
    How? What did you do?
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    I got 72.3kj/mol too. Double check your rearranging. To make it easier, rearrange before you put your numbers in.
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    (Original post by typicalvirgo)
    I got 72.3kj/mol too. Double check your rearranging. To make it easier, rearrange before you put your numbers in.
    -1 ((lnk x RT) - lnA)
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    I also got 73.2kj/mol. Show us the steps of your rearranging.
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    (Original post by spidle)
    I also got 73.2kj/mol. Show us the steps of your rearranging.
    ln6.51 x 10^-3 = ln2.57 x 10^10 - Ea / 8.31 x 300
    -12550.79... = ln2.57 x 10^10 - Ea
    Ea = ln2.57 x 10^10 + 12550.79...
    Ea = 12574.768... Jmol-1
    Ea = 12.6 kJmol-1 (3.s.f)
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    (Original post by kiiten)
    ln6.51 x 10^-3 = ln2.57 x 10^10 - Ea / 8.31 x 300
    -12550.79... = ln2.57 x 10^10 - Ea
    Ea = ln2.57 x 10^10 + 12550.79...
    Ea = 12574.768... Jmol-1
    Ea = 12.6 kJmol-1 (3.s.f)
    In step 2, you forgot to times In(2.57 x 10^10) by (8.31x300).
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    (Original post by kiiten)
    ln6.51 x 10^-3 = ln2.57 x 10^10 - Ea / 8.31 x 300
    -12550.79... = ln2.57 x 10^10 - Ea
    You went wrong at this part. You multiplied the whole left side by RT when it is only EA/RT on the right hand side, not (lnA-Ea/RT) but rather lnA-(Ea/RT).
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    (Original post by spidle)
    You went wrong at this part. You multiplied the whole left side by RT when it is only EA/RT on the right hand side, not (lnA-Ea/RT) but rather lnA-(Ea/RT).
    Oh so would it be:

    RT (lnA - lnk) = Ea
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    Yeah that's right. It should give you 72307J/mol so 72.3kJ/mol.
 
 
 
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