A polymer solution obeys the Mark-Houwink equation $ \eta = K M^{a} $ where $ \eta $ is the intrinsic viscosity, $ M $ is the viscosity‑average molecular weight, and the constants are $ K = 1.5 \times 10^{-4}\ \text{dL g}^{-1} $ and $ a = 0.75 $. An experiment measures an intrinsic viscosity of $0.85\ \text{dL g}^{-1}$ for the polymer.

(a) Calculate the viscosity‑average molecular weight $ M $ of the polymer.

(b) If the monomer unit has a molar mass of $100\ \text{g mol}^{-1}$, estimate the degree of polymerisation (DP) of the polymer.

Question

A polymer solution obeys the Mark-Houwink equation $ \eta = K M^{a} $ where $ \eta $ is the intrinsic viscosity, $ M $ is the viscosity‑average molecular weight, and the constants are $ K = 1.5 \times 10^{-4}\ \text{dL g}^{-1} $ and $ a = 0.75 $. An experiment measures an intrinsic viscosity of $0.85\ \text{dL g}^{-1}$ for the polymer.

(a) Calculate the viscosity‑average molecular weight $ M $ of the polymer.

(b) If the monomer unit has a molar mass of $100\ \text{g mol}^{-1}$, estimate the degree of polymerisation (DP) of the polymer.

Accepted Answer

M = 9.8×10^4 g mol^{-1}; DP ≈ 980

Igcse Model Questions Vol1 2019 Chemistry Question 25

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