A zero-order gas phase reaction A → B with rate (−r_A) = k = 100 mol/(L·min) is carried out in a mixed flow reactor of volume 1 L. Pure A is fed to the reactor at a rate of 1 mol/min. At time t=0, the outlet flow is stopped while the inlet flow rate and reactor temperature remain unchanged. Assume that the reactor was operating under steady state before the flow was stopped (t

Question

A zero-order gas phase reaction A → B with rate (−r_A) = k = 100 mol/(L·min) is carried out in a mixed flow reactor of volume 1 L. Pure A is fed to the reactor at a rate of 1 mol/min. At time t=0, the outlet flow is stopped while the inlet flow rate and reactor temperature remain unchanged. Assume that the reactor was operating under steady state before the flow was stopped (t<0). The rate of consumption of A, −dC_A/dt, in mol/(L·min), at t=1 min is

Accepted Answer

The correct answer is D, 99.0. GATE 2025 official key: (D). With the outlet closed, the reactor concentration decays exponentially toward the sustainable zero-order regime; evaluating the resulting consumption rate at t=1 min gives ≈99.0 mol/(L·min), per the official solution.