Q139 · CSIR-NET Chemistry, December 2019
Paper: CSIR-NET December 2019 · Subject: Physical Chemistry · Chapter: Polymer Chemistry · Topic: Viscometry Characterisation · Marks: 2 · Difficulty: Medium
Using standard equation for intrinsic viscosity $[\eta]=\mathrm{K} \overline{\mathrm{M}_{\mathrm{v}}^{\mathrm{a}}}$ for a solution of polymer and any information from the graph identify viscosity average molar mass $(\overline{\mathrm{M}})$ [given that $\mathrm{a}=0.5$, $\left.\mathrm{K}=5 \times 10^{-5} \mathrm{L} \mathrm{g}^{-1}\right)$ 
(a)$10^{3} \mathrm{g} / \mathrm{mol}$
(b)$10^{4} \mathrm{g} / \mathrm{mol}$
(c)$10^{5} \mathrm{g} / \mathrm{mol}$
(d)$10^{6} \mathrm{g} / \mathrm{mol}$
Answer
Answer: D ✓ checked by 4AB · confidence high
The source book printed C; on checking, D is correct — see the explanation.
Explanation
The intercept gives [η] = 0.050 L g⁻¹ = 5 × 10⁻⁵ M^0.5, so √M = 1000 and M = 10⁶ g mol⁻¹ (d).
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