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JEE 2012 Problem & Solution

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Solution

We have, \left( {P + \frac{{{n^2}a}}{{{V^2}}}} \right)\left( {V - nb} \right) = nRT

As per the question, \left( {P + \frac{a}{{{V^2}}}} \right)V = RT

\Rightarrow PV + \frac{a}{V} = RT

\Rightarrow PV = - a\frac{1}{V} + RT

Since PV is the y-axis and 1/V is the x-axis, slope=-a.

Slope = \frac{{20.1 - 21.6}}{{3.0 - 2.0}} = - 1.5 = - a

Thus,a = 1.5.

(C)