Terylene has the repeat unit -[O-CH2-CH2-O-CO-C6H4-CO]- (C10H8O4, 192 g/mol), made from ethylene glycol and terephthalic acid, HOOC-C6H4-COOH (166 g/mol). Neglecting end groups and assuming complete conversion, the mass of terephthalic acid needed to make 960 g of Terylene is

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JEE Advanced levelSingle correct optionDifficulty 3 of 3pl071

Terylene has the repeat unit $- [O - CH X_{2} - CH X_{2} - O - CO - C X_{6} H X_{4} - CO] X^{-}$ ( $C X_{10} H X_{8} O X_{4}$ , 192 g/mol), made from ethylene glycol and terephthalic acid, $HOOC - C X_{6} H X_{4} - COOH$ (166 g/mol). Neglecting end groups and assuming complete conversion, the mass of terephthalic acid needed to make $960 g$ of Terylene is

A960 g
B1140 g
C740 g
D830 g

Answer: D

Moles of repeat unit = 960/192 = 5.00. Each repeat unit uses one terephthalic acid, so mass = 5.00 x 166 = 830 g. The other options come from using the repeat-unit mass, the sum of both monomers, or subtracting one water per unit.

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Answer: D

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