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Homework Help: Diffusion of particles in batch reactors

  1. May 9, 2008 #1
    Hello everybody, I dont know if this is the right place to post this question. Sorry for that.

    I have the following system: small particles (I dont know exactly the composition) in a batch stilled tank reactor in which i add some hydrochloric acid.
    How I evaluate the concentration of saturation of those particles into the bulk?
    I am able to calculate the loss in volume vs time considering the total volume.
    I practice if we consider the solid particles as "A" and "Ca" the concentration of A, then I want to evaluate [Ca(saturation)-Ca(at a time t)] i am able to calculate Ca(at a time t) but i am not sure about Ca(saturation).
    I was thinking to consider Ca(saturation) as the concentration of all A dissolved into the bulk but I am not sure about it.

    Thanks very much, you can also write me at: dinodeblasio@yahoo.it
  2. jcsd
  3. May 9, 2008 #2


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    Homework Helper
    Gold Member

    Have you tried using the value of the solubility product of the ion A in water, to calculate the saturation concentration?

    Also, what is the HCl supposed to do? Does it react with the solid particles, or with whatever diffuses out from the solid?
    Last edited: May 9, 2008
  4. May 11, 2008 #3
    diffusion of solid particles

    Hello and thank you for answering,
    my solid is suppose to be some kind of limestone CaCO3, it reacts with HCl and releases Ca++ ions. In literature there are data on the concentration of saturation of Ca++ in water, but the value is too small because if i measure sperimentally the mass of solid lost and convert it to moles/liter, the moles of Ca++ should be much more. For this reason there is some other solid (impurities) that react with HCl or just dissolve into the water but in the mathematical model i dont know what concentration of saturation of Ca++ i should consider because in the mathematical model [Ca(saturation)-Ca(at time t)] must be positive.
    Is that completely wrong to consider the saturation for that system as the total moles of samples dissolved? The amount of acid I put into the reactor should be sufficient to dissolve all the Ca++, HCl is in a bit excess.
    Thanks again.
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