A sample experiment revealed that PVC formed in the medium has (Mn)=13, and (Mw)=16, where (Mn) stands for the number average molar mass and (Mw) for the weight average molar mass. The variance of Mn will then be

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 $\left(M_{n}\right)=13$, and $\left(M_{w}\right)=16$, where $\left(M_{n}\right)$ stands for the number average molar mass and $\left(M_{w}\right)$ for the weight average molar mass. The variance of $M_{n}$ will then be

(a)39

(b)3

(c)1

(d)87

Answer

Answer: A ✓ checked by 4AB · confidence high

Explanation

For a molar-mass distribution, variance = M_w·M_n − M_n² = 16 × 13 − 13² = 208 − 169 = 39.

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