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March 27, 2017

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Tricky one- my math fails here

(a) A pressure vessel contains a large volume of CO2 gas at 10 atm pressure. A membrane composed of a poly(ether ketone) polymer with thickness 100 microns and net effective area of 100 cm2 covers a small perforated port in the container. The solubility of CO2 at 10 atm is 6.97 x 10-4 moles/cm3 at 35 ∘C. The diffusivity of CO2 in the polymer is known to be 2.29 x 10-8 cm2/s at this temperature. How long will it take for 0.001 moles of CO2 to leak from the container at steady-state? Assume that the amount of carbon dioxide in the surroundings is insignificant. Express your answer in hours

(b) If the diffusivity is observed to double when the temperature is increased by 10 degrees C, what is the activation energy for diffusion? Express your answer in units of eV.

  • chemistry - ,

    I have no idea =/

  • chemistry - ,

    a) 1.74

  • chemistry - ,

    how about b

  • chemistry - ,

    I've got 1.14*10^19 applying known formula D=D0*exp[−EA/RT]but it's wrong. Who can write a formula for b?

  • chemistry - ,

    You have a ratio: D1/D2=1/2 and you know T1 and T2, use it.

  • chemistry - ,

    39.2 b

  • chemistry - ,

    Don't forget to convert your answer in eV

  • chemistry - ,

    39.2 is wrong answer. could you please help for the answer of b

  • chemistry - ,

    same here had 39.2 as the wrong answer.

  • chemistry - ,

    1ev= 1.69*10^-19 J

  • chemistry - ,

    You have a formula D=D0*exp[−EA/kT], you have a ratio D1/D2=1/2 and values of temperatures. Express EA and answer is yours.

  • chemistry - ,

    I multiply the Ea in 0.001 mole as the value is in j/moles. Still I don't get and how we apply two temparatures there?

  • chemistry - ,

    Stop cheating
    after the end of exam period i will tell you the answer

  • chemistry - ,

    You have a formula for D1 and for D2, you have a ratio D1/D2=1/2, further only answer)

  • chemistry - ,

    0.551

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