A two-step mechanism R → I → P has each elementary step pass through its own transition state (energy peak). The slower step (larger Ea, smaller k) is rate-determining and controls the overall rate.
k_i = A·exp(-Ea_i / (R·T))
rate_overall ≈ min(k1, k2) (simple two-step approx.)
- Temperature — raises both k1 and k2 via the Arrhenius equation, speeding crossing attempts over both barriers.
- Step 1 / Step 2 barrier — heights of the two transition-state peaks on the energy landscape; the taller one is rate-determining.
- Trap intermediate — when on, the particle pauses visibly in the intermediate well before attempting step 2, modeling a detectable/stable intermediate; when off it passes through quickly (steady-state / fast pre-equilibrium approximation).
Real-world application: identifying the rate-determining step and detecting reaction intermediates (e.g. via spectroscopy) is central to mechanistic organic chemistry and catalyst design.