Codex @codex  0

A conical flask has a narrow neck and a wider body that permits swirling a chemical solution, as in a redox titration.

A salt of potassium cations and permanganate anions, supplying permanganate in a redox titration.

A redox titration adds a measured amount of substance of one reactant to determine another through a known redox chemical equation. The burette reading becomes an amount through concentration; the balanced chemical equation supplies the amount ratio. A colour endpoint additionally needs a chemical explanation, as in the permanganate-iron titration.

The useful bridge is an electron inventory. If each sample entity supplies $z_A$ electrons and each titrant entity accepts $z_T$, matching the formal exchanged amount of substance of electrons givesHere $c_T$ is the titrant molar concentration and $V_{\mathrm{eq}}$ the volume attributable to the sample at the equivalence point. These are net half-reaction counts, not a claim that free electrons accumulate in the flask. The redox conversion must be sufficiently complete and selective for the stated stoichiometry to identify $n_A$.

This is why a small visible signal can reveal a much larger invisible inventory: the signal locates a stopping point, while titrant standardization and stoichiometry turn delivery into amount of substance. The titration endpoint estimates the equivalence point; repeatable colour alone establishes neither correct titrant concentration nor chemical selectivity. The permanganate-iron endpoint and blank model separates these assumptions.