Question

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Calculate the number-average molecular weight of a random nitrile rubber [polyacrylonitrile-butadiene) copolymer] in which the fraction of butadiene repeat units is 0.31: assume that this cancentration corresponds to a degree af polymerization of 2000. ? Part1 Calculate the molecular welght of the acrylonitrile repeat unit in a/mol click here to access Iable 14.5 Atomic weights for several elements are included in the following table Carbon12.01 g/mal Chlorine 35.45 g/mal Fluorine 19.00 a/mol Hydrogen 1.008 a/mo Oxygen 16.00 o/mol Nitrogen14.01 g/mol My: g/mol

Answer 1

Accylonitrite = c_3 H_3N contain 3 corbon atoms, 1 nitrogen atom and 3 hydrogen atoms this the molecular weight of accelyonite separate unit is m_AC = 3 (A_c) + (A_N) + 3 (A_4) M_AC = (3) (12.01) + (14.01) + 3(1.008) = 53.06 g/m butadiene separate unit have 4 carbons atom and 6 hydrogen atoms so molecule weight of butadiene repeat unit rightarrow m_Bu = 4(A_c) + 6 (A_4) = 4 (12.01) + 6(1.008) M_Bu = 54.09 g/ mol Now for the average repeat unit molecular weight rightarrow m ^- f_Bu m_Bu + f_Ac M_AC \r\n f_Bu = fraction of butadiene repeat unit Given = 0.31 To F_Ac will be (1 - 0.31) = 0.69 Now putting values for m ^- rightarrow m ^- (0.69) (53.06) + (0.31) (54.09) m ^- 53.37 g/mol Now for number average molecular weight rightarrow m ^- _n rightarrow Given degree of polymerization