Neco Model Questions Vol1 2021 Chemistry Question 48

An unknown polymer is dissolved in a suitable solvent at 25 °C. The measured intrinsic viscosity is \([\eta] = 0.85\ \text{dL g}^{-1}\). For this polymer‑solvent system the Mark-Houwink parameters are \(K = 1.2 \times 10^{-4}\ \text{dL g}^{-1}\) and \(a = 0.75\). The polymer is formed from ethylene monomer (\(\text{C}_2\text{H}_4\), \(M_{\text{mon}} = 28\ \text{g mol}^{-1}\)). (i) Calculate the viscosity‑average molecular weight \(M_{\text{v}}\) and the degree of polymerisation (DP). (ii) If 20 % of the monomer units are hydrolysed so that each hydrolysed unit gains an extra \(\text{O}\) atom and an extra \(\text{H}\) atom (changing a -CH₂- group to -COOH), determine the change in the mass percent of carbon in the polymer.