mass action rate law for second order forward, second order reverse, reversible reactions, two reactants mass action rate law for second order forward, second order reverse, reversible reactions, two reactants, one product, continuous scheme Reaction scheme where the products are created from the reactants and the change of a product quantity is proportional to the product of reactant activities. The reaction scheme does include a reverse process that creates the reactants from the products. The rate of the forward process is proportional to the product of two reactant quantities. The rate of the reverse process is proportional to the square of one product quantity. It is to be used in a reaction modelled using a continuous framework. <n0:math xmlns:n0="http://www.w3.org/1998/Math/MathML"> <n2:semantics xmlns:n2="http://biomodels.net/SBO/" definitionURL="http://biomodels.net/SBO/#SBO:0000062"> <n2:lambda> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000036">kf</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000039">kr</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000509">R1</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000509">R2</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000512">P</n2:ci></n2:bvar> <n2:apply> <n2:minus /> <n2:apply> <n2:times /> <n2:ci>kf</n2:ci> <n2:ci>R1</n2:ci> <n2:ci>R2</n2:ci> </n2:apply> <n2:apply> <n2:times /> <n2:ci>kr</n2:ci> <n2:ci>P</n2:ci> <n2:ci>P</n2:ci> </n2:apply> </n2:apply> </n2:lambda> </n2:semantics> </n0:math>