$word_{count}$: 200

Pseudo-first order: a reaction of true order > 1 behaves as first order when one or more reactants are in large excess. Classic example: acid hydrolysis of ester (CH3COOC2H5 + H2O). True rate = k[ester][H2O]. Since [H2O] ≈ 55.5 M (constant), rate = k'[ester] where k' = k[H2O]. k' is the pseudo-first order rate constant. Inversion of sucrose in dilute acid is another standard example — followed by optical rotation measurements. Complex reaction types: (1) Parallel (competing): A -> B (k1) and A -> C (k2). Overall: [A] decays with $k_{eff}$ = k1 + k2. Product ratio: [B]/[C] = $\frac{k1}{k2}$ (kinetic control). (2) Consecutive: A -> B -> C (k1, k2). B shows a maximum concentration at $t_{max}$ = ln$\frac{k1/k2}{(k1-k2)}$. If k2 >> k1, B is consumed as fast as formed (steady-state). If k1 >> k2, B accumulates. (3) Reversible: A ⇌ B (kf, kr). Equilibrium: K = $\frac{kf}{kr}$ = [B]_eq/[A]_eq. These types appear in JEE Advanced mechanism-based questions.