Question

question 4 consider a random nitrile rubber poly(acrylonitrile - butadiene) copolymer in which the fraction by number of butadiene repeat units is 0.34. calculate the average molecular weight of the copolymer repeat unit in g/mol. hint: you calculated the molecular weights of acrylonitrile and butadiene in the previous two questions. (overline{m}=) g/mol (2 decimal places) 1 pts

Explanation:

Step1: Determine the fraction of acrylonitrile

The fraction of butadiene is 0.34. Since the sum of the mole - fractions of the two components in a binary copolymer is 1, the mole - fraction of acrylonitrile ($x_{a}$) is $x_{a}=1 - 0.34=0.66$.

Step2: Assume molar masses of repeat units

The molar mass of the acrylonitrile repeat unit ($M_{a}$) is approximately 53 g/mol (C3H3N: $3\times12 + 3\times1+14 = 53$ g/mol), and the molar mass of the butadiene repeat unit ($M_{b}$) is approximately 54 g/mol (C4H6: $4\times12+6\times1 = 54$ g/mol).

Step3: Calculate the average molar mass

The formula for the average molar mass ($\overline{m}$) of a random copolymer is $\overline{m}=x_{a}M_{a}+x_{b}M_{b}$. Substitute $x_{a}=0.66$, $M_{a} = 53$ g/mol, $x_{b}=0.34$, and $M_{b}=54$ g/mol into the formula:
$\overline{m}=0.66\times53+0.34\times54$
$=0.66\times53 + 0.34\times(53 + 1)$
$=(0.66 + 0.34)\times53+0.34\times1$
$=53+0.34$
$=53.34$ g/mol

Answer:

53.34 g/mol