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Chapter 14: Problem 20

Crosslinked copolymers consisting of 35 wt \(\%\) (- ethylene and 65 wt \% propylene may have elastic properties similar to those for natural rubber. For a copolymer of this composition, determine the fraction of both repeat unit types.

Short Answer

Expert verified
Answer: The approximate mole fractions of ethylene and propylene in the crosslinked copolymer are 44.8% and 55.2%, respectively.

Step by step solution

01

Calculate the molar mass of ethylene and propylene

To determine the molar mass of ethylene (C2H4), we will count the number of carbon atoms (C) and hydrogen atoms (H) in the compound and multiply them by their respective atomic masses (M(C) = 12.01 g/mol and M(H) = 1.01 g/mol). Molar mass of ethylene (C2H4) = (2 × 12.01) + (4 × 1.01) = 24.02 + 4.04 = 28.06 g/mol Similarly, for propylene (C3H6): Molar mass of propylene (C3H6) = (3 × 12.01) + (6 × 1.01) = 36.03 + 6.06 = 42.09 g/mol
02

Calculate the mass of ethylene and propylene in 100 g of the copolymer

Since we are given the weight percentages of ethylene and propylene, we can assume that we have 100 g of the copolymer. Then, we can calculate the mass of each component using the weight percentages: Mass of ethylene = 35 wt% × 100 g = 35 g Mass of propylene = 65 wt% × 100 g = 65 g
03

Calculate the moles of ethylene and propylene in the copolymer

Now, we will determine the moles of ethylene and propylene in the copolymer using their respective molar masses: Moles of ethylene = mass / molar mass = 35 g / 28.06 g/mol ≈ 1.25 mol Moles of propylene = mass / molar mass = 65 g / 42.09 g/mol ≈ 1.54 mol
04

Calculate the mole fractions of ethylene and propylene

Finally, we can determine the mole fractions of ethylene and propylene in the copolymer. The mole fraction is the ratio of the moles of a component to the total moles in the mixture. Total moles in the copolymer = moles of ethylene + moles of propylene = 1.25 mol + 1.54 mol = 2.79 mol Mole fraction of ethylene = moles of ethylene / total moles = 1.25 mol / 2.79 mol ≈ 0.448 Mole fraction of propylene = moles of propylene / total moles = 1.54 mol / 2.79 mol ≈ 0.552 In summary, the fraction of both repeat unit types in the crosslinked copolymer is approximately 44.8% ethylene and 55.2% propylene.

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Most popular questions from this chapter

(a) Is it possible to grind up and reuse phenol- ( formaldehyde? Why or why not? (b) Is it possible to grind up and reuse polypropylene? Why or why not?

On the basis of the structures presented in this chapter, sketch repeat unit structures for the following polymers: (a) polychlorotrifluoroethylene (b) poly(vinyl alcohol)

(a) Determine the ratio of butadiene to acrylonitrile repeat units in a copolymer having a number-average molecular weight of \(250,000 \mathrm{~g} / \mathrm{mol}\) and a degree of polymerization of 4640 . (b) Which type(s) of copolymer(s) will this copolymer be, considering the following possibilities: random, alternating, graft, and block? Why?

A random poly(styrene-butadiene) copoly\(\Theta\) mer has a number-average molecular weight of \(350,000 \mathrm{~g} /\) mol and a degree of polymerization of 5000. Compute the fraction of styrene and butadiene repeat units in this copolymer.

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