Neco 2018 Chemistry Question 48

Practice objective / multiple choice question 48 from the 2018 Neco Chemistry examination.

Neco 2018 Chemistry Objective / Multiple Choice Hard Difficulty
Question 48 NECO • 2018 • CHEMISTRY • objective

A step‑growth polymerisation is carried out between a diacid (molar mass 146 g mol⁻¹) and a diamine (molar mass 60 g mol⁻¹) to give a polyamide. The reaction mixture contains 0.020 mol of the diacid and 0.018 mol of the diamine. After polymerisation the number‑average molecular weight \(M_{n}\) is measured as 12 000 g mol⁻¹. Assuming Carothers equation applies, (i) calculate the extent of reaction \(p\); (ii) determine the fraction of the initial diamine that remains unreacted; and (iii) state the theoretical maximum \(M_{n}\) if the monomers were present in exact stoichiometric balance and the reaction proceeded to completion.

Answer Options

A. (i) \\(p≈0.950\\) (95.0 %); (ii) ≈5.0 % of the initial diamine remains unreacted; (iii) theoretical \\(M_{n}\\) = 12 000 g mol⁻¹ (finite limit).
Correct Answer B. (i) \(p≈0.969\) (96.9 %); (ii) ≈3.1 % of the initial diamine remains unreacted; (iii) theoretical \(M_{n}\) → ∞ (no finite upper limit).
C. (i) \\(p≈0.985\\) (98.5 %); (ii) ≈1.5 % of the initial diamine remains unreacted; (iii) theoretical \\(M_{n}\\) → 0 (no polymer formed).
D. (i) \\(p≈0.900\\) (90.0 %); (ii) ≈10 % of the initial diamine remains unreacted; (iii) theoretical \\(M_{n}\\) = 1 200 g mol⁻¹ (limited by stoichiometry).
Correct Answer
B
Correct Option:
(i) \(p≈0.969\) (96.9 %); (ii) ≈3.1 % of the initial diamine remains unreacted; (iii) theoretical \(M_{n}\) → ∞ (no finite upper limit).

About This Question

This is Neco 2018 Chemistry Question 48. It is one of the objective questions from the 2018 Neco Chemistry examination.

Difficulty level: Hard .

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