The Ievlev multipoint probability density function closure proposal is applied at the two‐point level to the mass balance equation for a single stochastically distributed reactant undergoing molecular diffusion and nonlinear reaction. The solution is shown to satisfy the major realizability properties of a probability density function and to be unique. In the case of a linear reaction, it produces the exact solution for an initially multivariate normal distribution. By short‐time numerical integration of a second‐order reaction with diffusion, the solution is shown to represent molecular mixing more satisfactorily than do existing one‐point theories.