Igcse Model Questions Vol1 2018 Chemistry Question 20

Nylon‑6,6 is a condensation polymer formed from hexamethylenediamine \(\mathrm{C_6H_{16}N_2}\) (molar mass 116.21 g mol\(^{-1}\)) and adipic acid \(\mathrm{C_6H_{10}O_4}\) (molar mass 146.14 g mol\(^{-1}\)). Each repeat unit of nylon‑6,6 is produced by the reaction of one molecule of each monomer with the loss of one molecule of water \(\mathrm{H_2O}\) (18.02 g mol\(^{-1}\)). (a) If 150 g of hexamethylenediamine and 150 g of adipic acid are reacted, and the overall yield of polymer is 85 % of the theoretical amount, calculate the mass of nylon‑6,6 obtained. (b) The number‑average molecular weight (\(M_n\)) of the polymer sample is measured as 28 000 g mol\(^{-1}\). Determine the number‑average degree of polymerisation (DP) of the sample.