Q48 · CSIR-NET Chemistry, December 2019
Paper: CSIR-NET December 2019 · Subject: Physical Chemistry · Chapter: Polymer Chemistry · Topic: Viscometry Characterisation · Marks: 2 · Difficulty: Hard
Using standard equation for intrinsic viscosity $[\eta]=K\bar{M}_v^{a}$ for a solution of polymer and any information from the graph identify viscosity average molar mass $(\bar{M})$ [given that $a=0.5$, $K=5\times10^{-5}\,\mathrm{L\,g^{-1}}$) 
(a)$10^{3}\,\mathrm{g/mol}$
(b)$10^{4}\,\mathrm{g/mol}$
(c)$10^{5}\,\mathrm{g/mol}$
(d)$10^{6}\,\mathrm{g/mol}$
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed C; on checking, D is correct — see the explanation.
Explanation
Extrapolating η_sp/c to c = 0 gives [η] = 0.050 L g⁻¹. Then 0.050 = 5 × 10⁻⁵ M^0.5, so √M = 1000 and M = 10⁶ g mol⁻¹ (d).
Study loop for Polymer Chemistry