Q61 · CSIR NET Chemistry, December 2018
Paper: CSIR NET December 2018 · Subject: Physical Chemistry · Chapter: Polymer Chemistry · Topic: Polymer Chemistry – General · Marks: 2 · Difficulty: Medium
The contour and root mean square length (in nm ) of a polymer chain modelled as a random coil, with $\mathrm{N}=1000$ and $=150 \mathrm{pm}$, are closest to
(a)1.50 and 47.4
(b)15.0 and 4.74
(c)150 and 47.4
(d)150 and 4.74
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed A; on checking, D is correct — see the explanation.
Printed A; √1000 × 0.15 nm is 4.74 nm, not 47.4.
Explanation
Contour length = Nl = 1000 × 0.15 nm = 150 nm; rms end-to-end = √N l = 31.6 × 0.15 = 4.74 nm.
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