This chapter studies the effect of chemical reaction on transient hydrymagnetic and thermal behavior of free convection flow past a vertical plate embedded in a porous medium. The governing equations are solved numerically by applying finite difference method. The results are obtained for velocity, temperature concentration and skin-friction profiles. The numerical values are presented graphically for pertinent parameters like magnetic parameter (M), Prandtl number (Pr), Schmidt number (Sc), Permeable parameter (k), Buoyancy ratio parameter (N).