Stare diffusion and reaction. solute a is diffusing at unsteady state into a semi-infinite medium of pure b and undergoes a first-order reaction with b. sol- ute a is dilute. calculate the concentration cat points z = 0.4, and 10 mm from the surface for 1 x 10's physical property data are d. 1 x 10 ml = 1 x 10 cx0 = 10 kg molím'. also calculate the kg mol absorbed/m.