CCL: Question: arrhenius parameters with MOPAC

 Sent to CCL by: "Carlos Abraham Diaz" [cancerbero_85|hotmail.com]
 Hello. I need some help in the determination of the activation energy of this
 reaction:
   NH3  +      H3PO4         ------>   NH4H2PO4              +    H2O
 ammonia   phosphoric acid           ammonium  phosphate        water
 It's a neutralization and exothermic reaction. And however a fast raction rate
 (i can't measure with standard equipment) I assume that is a elementary
 reaction.
 My questions are:
 IT'S POSSIBLE CALCULATE THE Ea WITH MOPAC IN A NORMAL PC?
 THERE IS NOT EXPERIMENTAL DATA ABOUT THIS REACTION?
 I have the heats of formation of reagents and products and i tried the
 bell-evans-polanyi correlation:
 Ea = E* + BHf
 And i found for a exothermic reaction that
 Ea = 40 + 0.25Hf
 But the result is a negative Ea.
 I don't have so much knowledge in computational chemistry and i only need the
 numeric valor of the Ea and/or the reference.
 Thank you.
 Carlos Abraham Diaz
 cancerbero_85===hotmail.com
 Ciudad Obregon, Sonora, Mexico.