The effects of mass transfer and chemical reaction on the flow of a viscous incompressible and chemically reacting fluid past an impulsively started infinite vertical plate are studied. The non‐linear coupled equations of the problem are solved numerically using the explicit finite difference method. The mass transfer parameter has been given various values to include the presence of different gases like H2O, CO2etc. in air. The results characterising the skin‐friction and rate of heat transfer at the plate have been shown graphically.