Dear Student, In reversible reaction driving force and opposing forces have almost equal magnitude since system undergoes an very small change in every step.Therefore work done is maximum in reversible process. Wrev =-∫V1v2P dV But in case of irreversible process , the process is spontaneous there is a sudden change in the system as driving force is much larger than the opposing force. Work done in isothermal is more as system uses surrounding energy to carried out process while in case of adiabatic q= 0. So system uses its internal energy to do work. Regards