A PHBV chain contains HB and HV units in a 4 : 1 mole ratio. HB is -[O-CH(CH3)-CH2-CO]- (86 g/mol) and HV is -[O-CH(C2H5)-CH2-CO]- (100 g/mol). Neglecting end groups, the mass percent of HV units in the chain is closest to

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A PHBV chain contains HB and HV units in a 4 : 1 mole ratio. HB is $- [O - CH (CH X_{3}) - CH X_{2} - CO] X^{-}$ (86 g/mol) and HV is $- [O - CH (C X_{2} H X_{5}) - CH X_{2} - CO] X^{-}$ (100 g/mol). Neglecting end groups, the mass percent of HV units in the chain is closest to

For 5 units: mass = 4(86) + 100 = 444 g. HV percent = 100/444 x 100 = 22.5. The 20.0 value is the mole percent, not the mass percent.