3.5Composition of Functions

The worked Nernst-equation example first computes Q = [Co²⁺]/[Fe²⁺] = 0.077 from concentrations, then substitutes that number into Ecell = E° − (0.0592/n)log Q — an inner formula's output becomes an outer formula's input, exactly the evaluate-the-inside-function-first pattern §3.5 teaches, and skipping straight to log of the raw concentrations instead of log of Q first is the place this goes wrong.

The Nernst-equation calculation is a two-stage function chain, not a single formula: first build Q = [Cd²⁺]/[Ni²⁺] from the two given concentrations, then feed that output into log(Q) before scaling and subtracting from E° — the same compute-the-inner-function-first, then-apply-the-outer-function structure as any composed function f(g(x)), and skipping straight to log of a raw concentration instead of the ratio is the error this chain invites.