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Kinetics question

  1. May 4, 2015 #1
    1. The problem statement, all variables and given/known data
    The question says:
    The decomposition of a gas on a surface follows the rate law : Rate is proportional to ##\frac {kP}{1+kP}##, where ##P## is the pressure and ##k## is a constant. Find the order of the reaction at high pressure.

    2. Relevant equations


    3. The attempt at a solution
    In the solution they have said that since ##P## is high therefore ##kP>>>1## due to which rate is proportional to ##\frac {kP}{kP}=1## which means the rate is a constant so it is a zero order reaction. What I say is that since they don't known the value of ##k## how can they come to the conclusion that ##kP>>>1##? If we assume k to be equal to a very very small number such that ##1>>>kP## then their assumption fails, and the rate is not a constant.
    So am I right about this thing or making a mistake?
     
  2. jcsd
  3. May 4, 2015 #2
    If doesn't matter what the value of k is. If you take a high enough pressure, the order will approach zero.

    chet
     
  4. May 4, 2015 #3
    But if we leave that proven part (I. e if pressure is increased order will tend towards zero) and use only this :
    Rate is proportional to $$\frac {kP}{1+kP} $$
    Then isn't the value of ##k## important?
     
  5. May 4, 2015 #4
    Sure. At pressures less than on the order of 1/k.

    Chet
     
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