Neco Model Questions Vol1 2018 Chemistry Question 34

Practice objective / multiple choice question 34 from the 2018 Neco Model Questions Vol1 Chemistry examination.

Neco Model Questions Vol1 2018 Chemistry Objective / Multiple Choice Hard Difficulty
Question 34 NECO_MODEL_QUESTIONS_VOL1 • 2018 • CHEMISTRY • objective

A sample of polyethylene has a measured density of 0.92 g·cm^{-3}. The density of completely crystalline polyethylene is 0.95 g·cm^{-3} and that of the amorphous form is 0.86 g·cm^{-3}. (a) Determine the percent crystallinity of the sample. (b) If the melting point of 100\% crystalline polyethylene is 135\,°C and the melting point depression follows T_{m}=T_{m0}\bigl[1 - K(1 - X_{c})\bigr] with K = 0.20, calculate the observed melting point of the sample. Give X_{c} as a percentage (to one decimal place) and T_{m} to the nearest degree Celsius.

Answer Options

Correct Answer A. Percent crystallinity = 66.7 %; melting point ≈ 126 °C
B. Percent crystallinity = 72.5 %; melting point ≈ 131 °C
C. Percent crystallinity = 60.0 %; melting point ≈ 123 °C
D. Percent crystallinity = 55.0 %; melting point ≈ 119 °C
Correct Answer
A
Correct Option:
Percent crystallinity = 66.7 %; melting point ≈ 126 °C

About This Question

This is Neco Model Questions Vol1 2018 Chemistry Question 34. It is one of the objective questions from the 2018 Neco Model Questions Vol1 Chemistry examination.

Difficulty level: Hard .

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