mass action rate law for first order forward, second order reverse, reversible reactions mass action rate law for first order forward, second order reverse, reversible reactions, two products, 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 quantity of one reactant. The rate of the reverse process is proportional to the product of two product quantities. 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:0000035">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">R</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000512">P1</n2:ci></n2:bvar> <n2:bvar><n2:ci definitionURL="http://biomodels.net/SBO/#SBO:0000512">P2</n2:ci></n2:bvar> <n2:apply> <n2:minus /> <n2:apply> <n2:times /> <n2:ci>kf</n2:ci> <n2:ci>R</n2:ci> </n2:apply> <n2:apply> <n2:times /> <n2:ci>kr</n2:ci> <n2:ci>P1</n2:ci> <n2:ci>P2</n2:ci> </n2:apply> </n2:apply> </n2:lambda> </n2:semantics> </n0:math>