A sample of 680 g of polyisoprene (repeat unit C5H8, 68 g/mol) is vulcanised so that there is one -S-S- bridge (two sulfur atoms, S = 32) for every 100 isoprene repeat units. The mass of sulfur consumed is

JEE Advanced levelSingle correct optionDifficulty 3 of 3pl089

A sample of 680 g of polyisoprene (repeat unit $C X_{5} H X_{8}$ , 68 g/mol) is vulcanised so that there is one $- S - S X^{-}$ bridge (two sulfur atoms, S = 32) for every 100 isoprene repeat units. The mass of sulfur consumed is

Repeat units = 680/68 = 10.0 mol. Cross-links = 10.0/100 = 0.10 mol. Each bridge uses 2 S, so S = 0.20 mol x 32 = 6.4 g.