A sample of polystyrene (repeat unit -[CH2-CH(C6H5)]-, taken as 104 g mol^-1) has M_n = 1.04x10^5 g mol^-1. The number-average degree of polymerisation is

JEE Main levelSingle correct optionDifficulty 2 of 3pl030

A sample of polystyrene (repeat unit $- [CH X_{2} - CH (C X_{6} H X_{5})] X^{-}$ , taken as 104 $g mo l^{- 1}$ ) has $M_{n} = 1.04 \times 1 0^{5} g mo l^{- 1}$ . The number-average degree of polymerisation is

D P_{n} = M_{n} / M_{0} = 1.04 \times 1 0^{5} /104 = 1000

repeat units, since each styrene unit adds 104 to the chain mass.