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ChemistryNEET 2025Conductance and Kohlrausch's law

Electrochemistry

If the molar conductivity (Λm\Lambda_m) of a 0.050 mol L−10.050\ \mathrm{mol\,L^{-1}} solution of a monobasic weak acid is 90 S cm2 mol−190\ \mathrm{S\,cm^2\,mol^{-1}}, its extent (degree) of dissociation will be [assume λ+∘=349.6 S cm2 mol−1\lambda^\circ_{+} = 349.6\ \mathrm{S\,cm^2\,mol^{-1}} and λ−∘=50.4 S cm2 mol−1\lambda^\circ_{-} = 50.4\ \mathrm{S\,cm^2\,mol^{-1}}]:

  1. A.0.115
  2. B.0.125
  3. C.0.225✓
  4. D.0.215

Solution

Λm∘=349.6+50.4=400 S cm2 mol−1\Lambda_m^\circ = 349.6 + 50.4 = 400\ \mathrm{S\,cm^2\,mol^{-1}}. Degree of dissociation α=ΛmΛm∘=90400=0.225\alpha = \frac{\Lambda_m}{\Lambda_m^\circ} = \frac{90}{400} = 0.225.

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