A titration measures a concentration you cannot see by reacting it away with one you know. A measured aliquot of the unknown acid (volume $V_a$) waits in the flask; a standard base (concentration $C_b$) drips from the burette until the indicator turns — the equivalence point, where the moles have exactly annihilated each other. At that instant $C_a V_a = n\,C_b V_b$ — read aloud: C-a V-a equals n C-b V-b, where $n$ is the mole ratio, moles of acid per mole of base.

For HCl against NaOH the dance is one-to-one: $n = 1$. Sulfuric acid brings TWO protons per molecule, so each acid particle spends two of the base: $n = 0.5$. And since $V_a$ and $V_b$ meet as a ratio, millilitres cancel millilitres — the one formula in this chapter where nobody converts anything.