GATE 2023 CH – Question 58

Fresh catalyst is loaded into a reactor before the start of the following catalytic reaction. $A \longrightarrow products$
The catalyst gets deactivated over time. The instantaneous activity $a(t)$, at time $t$, is defined as the ratio of the rate of reaction $-r_A'(t)$ (mol (g cat)$^{-1}$hr$^{-1}$) to the rate of reaction with fresh catalyst. Controlled experimental measurements led to an empirical correlation $-r_A'(t) = -0.5t + 10$ where $t$ is in hours. The activity of the catalyst at $t = 10$ hr is _______ (rounded off to one decimal place).