Answer:
106,504 g/mol
Explanation:
The two repeat units at the polymer are the acrylonitrile and the butadiene. If the fraction of repeat of butadiene is 0.27, the fraction of repeat of units of acrylonitrile must be 0.73.
The acrylonitrile repeat unit has 3 carbons atoms, 1 nitrogen atom, and 3 hydrogen atoms. So, the molecular weigth for it is:
mac = 3*mC + 1*mN + 3*mH
mC = 12 g/mol; mN = 14 g/mol; mH = 1g/mol
mac = 3*12 + 14 + 3*1 = 53 g/mol
The butadiene repeat unit has 4 carbons atoms and 6 hydrogen atoms. Thus, the molecular weight is:
mbu = 4*12 + 6*1 = 54 g/mol
The average repeat unit molecular weight is the fractions multiplied by the molecular weight of the repeat unities:
m = 0.73*53 + 0.27*54 = 53.27 g/mol
The number-average molecular weight is the average repeat unit molecular weight multiplied by the degree of polymerization:
M = 53.27*2000
M = 106,504 g/mol
