Diffusively limited chemical reactions between initially separated reactants occur at the interfaces between them during mixing. We study such reactions in two-dimensional electromagnetically driven fluid flows exhibiting chaotic advection, for a variety of flow patterns and, Reynolds numbers. By measuring the stretching field of the flow, which is essentially the field of finite time Lyapunov exponents, we show that the extent of the acid-base chemical reaction can be predicted. A single parameter, the product of the mean Lyapunov exponent and the number N of mixing cycles, can be used to predict the time-dependent total product for flows having different dynamical features.*

* Phys. Rev. Lett., 96, 024501 (2006)