The rate constant of the reaction A→B is 0.6×10-3 mol L-1 s-1. If the concentraction of A is 5M  then concentration of B after  20  minutes is

Reaction is of zero order as the unit of rate constant is mol L-1s-1amount of A left = amount of B formed                   a-x =x∴   Concentration of B=k×t=0.6×10-3×20×60                                                     = 0.72 M