This is the boss. No calculator — today $\ln 2 = 0.70$, the working chemist's rounding, and every draw is chosen to fit in your head. One tank, one long problem, and every answer feeds the next: the rate constant from the logged rate, then the warmed constant, then the half-life it buys, then what survives the hold — and finally the only thing the plant actually cares about, which is whether the batch may be discharged. Write each line down as you go; one early slip rolls all the way to the verdict.

The chapter rides in it. The rate law reads backwards to give $k$. The ten-degree rule — a rate constant that DOUBLES for a 10 K rise, which is what a typical activation energy of about 50 kJ/mol buys you near room temperature — moves $k$ without ever needing $A$, because $A$ cancelled the moment two temperatures were compared. Then $t_{1/2} = \ln 2 / k$, then the halvings.

5★ under par here is the chapter crown. Clock in.