Solute A is diffusing at unsteady state into a semi$-$infinite medium of pure B and undergoes a first$-$order reaction with B$.$ Solute A is dilute. Calculate the concentration cA at points z $=0,4,$ and $10$ mm from the surface for t $=1\backslash$times $105$ s$.$ Physical property data are DAB $=1\backslash$times $109$ m$2/$s$,$ k $=1\backslash$times $104$ s$1,$ cA$0=1\mathrm{.}0$ kg mol A$/$m$3.$ Also calculate the kg mol A absorbed$/$m$2.$