Q31 · CSIR NET Chemistry, December 2014
Paper: CSIR NET December 2014 · Subject: Physical Chemistry · Chapter: Polymer Chemistry · Topic: Molecular Weight Averages · Marks: 2 · Difficulty: Medium
A sample experiment revealed that PVC formed in the medium has $(M_n) = 13$, and $(M_w) = 16$, where $(M_n)$ stands for the number average molar mass and $(M_w)$ for the weight average molar mass. The variance of $M_n$ will then be
(a)39
(b)3
(c)1
(d)87
Answer
Answer (as printed): A
Explanation
Variance = (Difference between molar mass and weight molar mass) ×molar mass = (16-3)× 13 = 3×13=39 Here molar mass represented xi and weighted molar mass fi . In this question data set and there frequency is not given. All the final values are given. So, variance = 𝐸 𝑥 Z − 𝐸(𝑥)
Explanation as extracted from the printed page; notation may be imperfect.
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