This is the boss. No calculator. Every concentration in the cascade is pinned to an exact power of ten, so every logarithm is mental: the pH of $1 \times 10^{-k}$ is $k$, and halving an even exponent is the hardest arithmetic on the page. One bench runs the whole unit: the volumetric flask dilutes the titrant, the burette finds the acid, the log places it on the scale, the see-saw hands over the other end — and every answer feeds the next line. Write each line down. A wrong dilution rides all the way to a wrong pH, and the finish will trace exactly where the cascade started to slip.

Then the last question does what real chemistry always does: it asks you to decide. A number is not an answer until it has been ruled on. 5★ under par here is the chapter crown. Goggles on, clock in.