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maksim [4K]
3 years ago
7

2. Calculate the number-average molecular weight of a random poly (isobutylene-isoprene) copolymer in which the fraction of isob

utylene repeat units is 0.25; assume that this concentration corresponds to a degree of polymerization of 1500.
Chemistry
1 answer:
Phoenix [80]3 years ago
5 0

Answer : The number-average molecular weight is, 97500 g/mol

Explanation :

First we have to calculate the molecular weight of isobutylene and isoprene.

The molecular formula of isobutylene and isoprene is, C_4H_8 and C_5H_8

Molecular weight of C_4H_8 = 4(12 g//mol) + 8(1 g/mol) = 56 g/mol

Molecular weight of C_5H_8 = 5(12 g//mol) + 8(1 g/mol) = 68 g/mol

Now we have to calculate the average repeat molecular weight.

Average repeat molecular weight = 0.25\times (56g/mol)+(1-0.25)\times (68g/mol)

Average repeat molecular weight = 65 g/mol

Now we have to calculate the number-average molecular weight.

Number-average molecular weight = Average repeat molecular weight × Degree of polymerization

Number-average molecular weight = (65 g/mol) × (1500)

Number-average molecular weight = 97500 g/mol

Thus, the number-average molecular weight is, 97500 g/mol

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