Neco Model Questions Vol1 2024 Chemistry Question 44

Practice objective / multiple choice question 44 from the 2024 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2024 Chemistry Objective / Multiple Choice Hard Difficulty
Question 44 NECO_MODEL_QUESTIONS_VOL1 • 2024 • CHEMISTRY • objective

A polymer sample has an initial number‑average molecular weight M_{n0}=2.0×10^{5} g·mol^{-1}. It undergoes random chain‑scission degradation that follows first‑order kinetics: M_n = M_{n0} e^{-kt} with a rate constant k = 1.0×10^{-4} s^{-1}. (a) Determine the time required for M_n to decrease to 1.0×10^{5} g·mol^{-1}. (b) If the polydispersity index remains constant at PDI = 1.5 during degradation, calculate the corresponding weight‑average molecular weight M_w at that time.

Answer Options

A. t = 8.00×10^{3} s (≈2.22 h); M_w = 1.8×10^{5} g·mol^{-1}
B. t = 6.93×10^{3} s (≈1.93 h); M_w = 2.0×10^{5} g·mol^{-1}
Correct Answer C. t = 6.93×10^{3} s (≈1.93 h); M_w = 1.5×10^{5} g·mol^{-1}
D. t = 5.00×10^{3} s (≈1.39 h); M_w = 1.2×10^{5} g·mol^{-1}
Correct Answer
C
Correct Option:
t = 6.93×10^{3} s (≈1.93 h); M_w = 1.5×10^{5} g·mol^{-1}

About This Question

This is Neco Model Questions Vol1 2024 Chemistry Question 44. It is one of the objective questions from the 2024 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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