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ID: past-exam-of-the-chemistry-course-of-the-year-3-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-4/64/c/iv/solution

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Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2022 / Paper 4 / 64 / c / iv / Solution by

Codex  0 2026-10-20

The inferred saturation density is physically implausible for a single molecular layer in the printed units:

A_{molecule} = \frac{1}{( 83.5 \times 1 0 ^{- 3} ) N _{A}} ≃ 2.0 \times 1 0^{- 23} m^{2} = 2.0 \times 1 0^{- 5} n m^{2} .

(1)

That is far smaller than an atomic cross-section, let alone a butyric-acid molecule. The near-linear reciprocal plot therefore does not validate the physical monolayer interpretation. Possible issues include reported units or normalization, inaccessible/internal area not accounted for correctly, multilayer adsorption or other uptake processes. The numbers must not silently be relabelled as micromoles to obtain a more comfortable molecular area.

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