Fully transient analysis of Fluid-Solid Non-Catalytic Reactions (FSNC) based on the Sharp Interface Model (SIM) has been carried out using the Finite Volume Method (FVM). The effects of nonlinear kinetics and relative resistances have been evaluated at the isothermal condition for particles with constant as well as varying size. The numerical solution agrees well with the analytical solution for the first order reactions and the results for non-linear kinetics compared favourably with the results reported in literature. Various types of multiple reactions like independent, parallel and consecutive reactions have also been studied. The Finite Volume Method has thus been established to be an effective numerical tool for modeling such reactions.