Reaction rate constants are critical factors for chemical kinetic model of trace elements,but there are few studies on it to date.Most of them concentrated on the reaction rate constants which were from single point temperature;however,real chemical reaction processes are not on a point.The geometry optimizations of molecules,which are connected with the two reactions we studied,were firstly made by the quantum chemistry MP2 method at SDD basis function level.Meanwhile enthalpy,Gibbs free energy and frequencies are obtained.Furthermore,reaction rate constants are calculated in the temperature range from 200 K to 2 000 K,neither from experimental data nor by estimated,but directly from quantum chemistry software-Khimera(using transition state theory).Contrasting with the literature,present results are consistent with them.The results of this study indicates that the software-Khimera,using quantum chemistry theory,is an effective means for investigating reaction rate constants of trace element mercury and so on.