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The number average molecular mass and mass average molecular mass of a polymer are respectively 30,000 and 40,000. The poly dispersity index of the polymer is

$\begin {array} {1 1} (a)\;< 1 & \quad (b)\;> 1 \\ (c)\;1 & \quad (d)\;0 \end {array}$


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The dispersity from polymerization is often denoted as $ D =\large\frac{M_w}{M_n}$ , where $ M_w$ is the weight average molecular weight and $ M_n$ is the number average molecular weight. $ M_n$ is more sensitive to molecules of low molecular mass, while $M_w$ is more sensitive to molecules of high molecular mass
Here $D=\large\frac{40,000}{30,000} $which is $ >1$
Ans : (b)
answered Mar 12, 2014 by thanvigandhi_1

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