Int. J. Pure Appl. Sci. Technol., 3(1) (2011), pp. 19-26 International Journal of Pure and Applied Sciences and Technology ISSN 2229 - 6107 Available online at www.ijopaasat.in Research Paper First Order Chemical Reaction on Isothermal Vertical Oscillating Plate with Variable Mass Diffusion R. Muthucumaraswamy 1, * and K. Manivannan 2 1 Department of Applied Mathematics, Sri Venkateswara College of Engineering, Pennalur, Sriperumbudur 602105, INDIA. 2 RMK Enginnering College, Kaverapettai, Gumidipoondi.  Corresponding author, e-mail: msamy@svce.ac.in (Received: 29-11-2010; Accepted: 22-12-2010) Abstract: Unsteady free convective flow of a viscous incompressible flow past an infinite isothermal vertical oscillating plate with variable mass diffusion is presented here, taking into account of the homogeneous chemical reaction of first-order. The plate temperature is raised to w T and the concentration level near the plate is raised linearly with respect to time. An exact solution to the dimensionless governing equations has been obtained by the Laplace transform method, when the plate is oscillating harmonically in its own plane. The effects of velocity and concentration are studied for different parameters like phase angle, chemical reaction parameter, Schmidt number and time are studied. It is observed that the velocity increases with decreasing phase angle t ω or chemical reaction parameter Keywords : chemical reaction, oscillating, vertical plate, heat and mass transfer. 1. Introduction The Effect of a chemical reaction depend whether the reaction is homogeneous or heterogeneous. This depends on whether they occur at an interface or as a single phase volume reaction. In well-mixed systems, the reaction is heterogeneous, if it takes place