Nylon 2-nylon 6 is made from glycine and 6-aminohexanoic acid, H2N-(CH2)5-COOH (131 g/mol), in 1 : 1 ratio. The repeat unit -[NH-CH2-CO-NH-(CH2)5-CO]- has a mass of 170 g/mol. Neglecting end groups and assuming complete conversion, the mass of 6-aminohexanoic acid needed for 1.70 kg of polymer is

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Nylon 2-nylon 6 is made from glycine and 6-aminohexanoic acid, $H X_{2} N - (CH X_{2}) X_{5} - COOH$ (131 g/mol), in 1 : 1 ratio. The repeat unit $- [NH - CH X_{2} - CO - NH - (CH X_{2}) X_{5} - CO] X^{-}$ has a mass of 170 g/mol. Neglecting end groups and assuming complete conversion, the mass of 6-aminohexanoic acid needed for 1.70 kg of polymer is

A1130 g
B1081 g
C1700 g
D1310 g

Answer: D

1700/170 = 10.0 mol of repeat units, each using one 6-aminohexanoic acid: 10.0 x 131 = 1310 g. The 1081 g option wrongly splits the polymer mass in the ratio of the monomer masses, ignoring the water lost.

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Answer: D

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