An investigation of the effects of a chemical reaction and thermal radiation on unsteady MHD free convection heat and mass transfer flow of an electrically conducting, viscous, incompressible fluid past a vertical infinite flat plate embedded in a porous medium is carried out. The flow is induced by a general time-dependent movement of the vertical plate, and the cases of ramped temperature and isothermal plates are studied. An exact solution of the governing equations is obtained in closed form by the Laplace Transform technique. Some applications of practical interest for different types of plate motions are discussed. The numerical values of fluid velocity, temperature and species concentration are displayed graphically whereas the numerical values of skin friction, Nusselt number and Sherwood number are presented in a tabular form for various values of pertinent flow parameters for both ramped temperature and isothermal plates.
 Nield D.A. and Bejan A. (1998): Convection in porous media, 2nd Edition. - Berlin: Springer-Verlag.
 Hiremath P.S. and Patil P.M. (1993): Free convection effects on oscillatory flow of couple stress field through a porous medium. - ACTA Mechanica, vol.98, No.1-4, pp.143-158.
 Muthucumaraswamy R. and Valli-Ammal V. (2010): The theoretical study of unsteady flow past an exponentially accelerated infinite isothermal vertical plate with variable mass diffusion in the presence of homogeneous chemical reaction of first order. - Theo. Appl. Mech., vol.37, No.4, pp.251-262.
 Das U.N., Deka R. and Soungalgekar V.M. (1994): Effects on mass transfer on flow past an impulsively started infinite vertical plate with constant heat flux and chemical reaction. - Forschungim Ingenieurwesen, vol.60, pp.284-287.
 Suneetha S., Bhaskar Reddy N. and Ramachandra Prasad V. (2009): Effects of thermal radiation on the natural convective heat and mass transfer of a viscous incompressible gray absorbing-emitting fluid flowing past an impulsively started moving vertical plate with viscous dissipation. - Thermal Science, vol.13, No.2, pp.71-181.
 Satter M.A. and Kalim H. (1996): Unsteady free-convection interaction with thermal radiation in a boundary layer flow past a vertical porous plate. - J. Math. Phys. Sci., vol.30, No.1, pp.25-37.
 Aydin O. and Kaya A. (2008): Radiation effect on MHD mixed convection flow about a permeable vertical plate. - Heat Mass Transfer, vol.45, pp.239-246.
 Arpaci V.S. (1968): Effects of thermal radiation on the laminar free convection from a heated vertical plate. - Int. J. Heat Mass Transfer, vol.11, pp.871-881.
 Cess R.D. (1966): Interaction of thermal radiation with free convection heat transfer. - Int. J. Heat Mass Transfer, vol.9, pp.1269-1277.
 Cheng E.H. and Ozisik M.N. (1972): Radiation with free convection in an absorbing emitting and scattering medium. - Int. J. Heat Mass Transfer, vol.15, pp.1243-1252.
 Raptis A. (1998): Radiation and free convection flow through a porous medium. - Int. Comm. Heat Mass Transfer, vol.25, No.2, pp.289-295.
 Hossain M.A. and Takhar H.S. (1996): Radiation effects on mixed convection along a vertical plate with uniform surface temperature. - Heat Mass Transfer, vol.31, pp.243-248.
 Hossain M.A. and Takhar H.S. (1999): Thermal radiation effects on the natural convection flow over an isothermal horizontal plate. - Heat Mass Transfer, vol.35, pp.321-326.
 Das U.N., Deka R. and Soungalgekar V.M. (1996): Radiation effects on flow past an impulsively started vertical plate-an exact solution. - J. Theo. Appl. Fluid Mech., vol.1, No.2, pp.111-115.
 Ahmed T. and Alam Md Mahmud (2013): Finite difference solution of MHD mixed convection flow with heat generation and chemical reaction. - Proc. Eng., vol.56, pp.149-156.
 Seth G.S., Sarkar S. and Hussain S.M. (2014): Effects of Hall current, radiation and rotation on natural convection heat and mass transfer flow past a moving vertical plate. - Ain Shams Eng. Journal, vol.5, No.2, pp.489-503.
 Cookey C.I., Ogulu A. and Omubo Pepple V.B. (2003): Influence of viscous dissipation and radiation on unsteady MHD free convection flow past an infinite heated vertical plate in a porous medium with time-dependent suction. - Int. J. Heat Mass Transfer, vol.46, pp.2305-2311.
 Suneetha S., Bhaskar Reddy N. and Ramachandra Prasad V. (2008): Thermal radiation effects on MHD free convection flow past an impulsively started vertical plate with variable surface temperature and concentration. - J. Naval Archit. Marine Eng., vol.5, No.2, pp.57-70.
 Mahmoud M.A.A. (2009): Thermal radiation effect on unsteady MHD free convection flow past a vertical plate with temperature dependent viscosity. - Can J. Chem. Eng., vol.87, pp.47-52.
 Seth G.S., Nandkeolyar R. and Ansari Mds. (2013): Effects of thermal radiation and rotation on unsteady hydromagnetic free convection flow past an impulsively moving vertical plate with ramped temperature in a porous medium. - J. Appl. Fluid Mech., vol.6, pp.27-38.
 Huges W.F. and Yong F.J. (1966): The electro-Magneto-Dynamics of fluids. - New York, USA: John Wiley & Sons.
 Sacheti N.C., Chandraan P. and Singh A.K. (1994): Exact solution for unsteady MHD free convection flow on an impulsively started vertical plate with constant heat flux. - Int. Comm., Heat Mass Transfer, vol.21, No.1, pp.131-142.
 Takhar H.S., Gorla R.S.R. and Soundalgekar V.M. (1996): Effect of radiation on MHD free convection flow past a semi-infinite vertical plate using Runge-Kutta-Merson quadrature. - Int. J. Numerical Methods for Heat & Fluid Flow, vol.6, pp.77-83.
 Abd-El-Naby M.A., Elasayed M.E., Elbarbary N.Y. and Abdelzem (2003): Effects of radiation on MHD unsteady free convection flow over a vertical plate with variable surface temperature. - J. Appl. Math, vol.2, pp.65-86.
 Kishore P.M., Prasad Rao N.V.R.V., Varma S.V.K. and Venkataramana S. (2013): The effects of radiation and chemical reaction on unsteady MHD free convection flow of viscous fluid past an exponentially accelerated vertical plate. - Int. J. of Physical and Mathematical Sci., vol.4, No.1, pp.300-317.
 El-Fayez F.M.N. (2012): Effects of chemical reaction on the unsteady free convection flow past an infinite vertical permeable moving plate with variable temperature. - J. of Surface Engineered Materials and Adv. Tech., vol.2, pp.100-109.
 Sekhar D.V. and Reddy G.V. (2012): Effects of chemical reaction on MHD free convective oscillatory flow past a porous plate with viscous dissipation and heat sink. - Adv. in Appl. Sci. Res., vol.3, No.5, pp.3206-3215.
 Shateyi S. and Marewo G.T. (2014): Numerical analysis of unsteady MHD flow near a stagnation point of a twodimensional porous body with heat and mass transfer, thermal radiation and chemical reaction. - Boundary Value Problems, 2014:218.
 Nandkeolyar R., Das M. and Sibanda P. (2013): Exact solutions of unsteady MHD free convection in a heat absorbing fluid flow past a flat plate with ramped wall temperature. - Boundary Value Problems, vol.1, pp.1-16.
 Cramer K. and Pai S. (1973): Magnetofluiddynamics for Engineers and Applied Physicists. - New York: McGraw- Hill.
 Meyer R.C. (1958): On reducing aerodynamic heat-transfer rates by magnetohydrodynamic techniques. - J. Aeronaut. Sci., vol.25, pp.561-572.