# Multiphase Reaction (Mass Arrhenius)

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 August 26, 2010, 03:49 Multiphase Reaction (Mass Arrhenius) #1 New Member   Join Date: Jun 2010 Posts: 2 Rep Power: 0 hey everyone, i am working actually with an euler/lagrange simulation in ansys cfx 12.1 and i want to establish a reaktion inside a lagrage liquid droplet. The reaktions works with multiphase reaktion (mass arrhenisu). The Problem is that i don't know how to convert the pre exponential faktor from molebase arrhenius to a massbased. Can anyone help me? GreatDee likes this.

 August 26, 2010, 16:05 #2 New Member   Alex Join Date: Mar 2010 Location: Russia Posts: 19 Rep Power: 9 I'm not sure, but try this: 1) for 2 reactants the rate is: w = k*c1*c2 where k - Arrhenius reaction rate, c1 [mole/m3], c2 [mole/m3] - reactants concentrations 2) use molar weight of reactants mw1, mw2 [kg/mole] from periodic table. 3) some transformations: w = k [mole^-2 m^6 s^-1] * c1 [mole m^-3]* c2 [mole m^-3] = k1 [mole^-2 m^6 s^-1] * w1 [kg mole^-1] * c1 [mole m^-3]* w2 [kg mole^-1] * c2 [mole m^-3] where k1 = k / (w1*w2) [kg^-2 m^6 s^-1 ] and if the activation temperature and the temperature exponent is the same, the pre-exponential factor A1 = A / (w1*w2). Good luck a.m.

 August 30, 2010, 03:48 #3 New Member   Join Date: Jun 2010 Posts: 2 Rep Power: 0 thanks so far. I have a equlibrium reaction. One reaction ist SO2 (liq) -> H Ion + HSO3 Ion k = 3.265E16 [s^-1] transformed -> k* = k / M_SO2 The second reaction is H Ion + HSO3 Ion -> SO2 (liq) k2 = k / Keq [m^3 s^-1 mol^-1] K eq is the equlibrium constant of the reactions transformed -> k2* = k2 / (M_H * M_HSO3) is this the right transformation? Ativation Engery is the same is both reactions and Temperature Exponent ist Zero. for some reason the expected equilibrium does not work out in the simulation. thanks for your help

 August 30, 2010, 16:21 #4 New Member   Alex Join Date: Mar 2010 Location: Russia Posts: 19 Rep Power: 9 1) if the reaction is SO2 = H + HSO3, then equilibrium is wf = wb --> k1*c(SO2)= k2*c(H)*c(HSO3), where k1 = 3.265E16 [s^-1]. 2) therefore k2 = k1 * {c(SO2)/(c(H)*c(HSO3))} and keq = {c(SO2)/(c(H)*c(HSO3))} ----> k2 = k1 *keq for this reaction, keq must have a dimension (like [kg/m3]). There is another reaction (equilibrium): H2O(liq) + SO2(gas) =(1)= H2SO3 =(2)= H + HSO3 =(3)= 2H + SO3. In point of fact there are 3 equilibriums because H2SO3 is unstable. In this case k2eq = 0.02, k3eq = 6*10^-8. k1eq = 16 [mole/m3] = [SO2]*[H2O]/[H2SO3]=0.225[kg/m3]. If this case is suitable, you should use k1eq in spite of keq in order to find k2 (see p 2).

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