This paper aims to examine the influences of a binary chemical reaction and Arrhenius activated energy on the unsteady external flow with a stagnation point over a vertical stretched surface. The worked suspension is Casson non-Newtonian nanofluids, and two-phase nanofluid formulation is considered. Here, the nanoparticles near the surface are passively controlled, and the viscous dissipation and Joule heating impacts are assumed. Non-similar solutions are introduced and solved using Blottner technique based on finite difference method. It is focused on the system entropy, thickness of the thermal and mass boundary layers. The major findings show that the radiation parameter enhances the irreversibility owing to the heat transfer, and hence, the Bejan coefficient is rising. Also, the velocity ratio rising causes a diminishing in the skin friction coefficient.