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Indian Forest Service (Mains)

Chemistry optional

  • 2 papers
  • 200 marks each
  • 3 h per paper

Paper I covers physical and inorganic chemistry.

Indian Forest Service (Mains), Chemistry optional · 2024 · Paper I

Q4(b). Mean ionic activity coefficients

Question

Calculate the mean ionic activity coefficient γ± of (i) NaCl at molality 0.01 and (ii) Na₂SO₄ at molality 0.001 in aqueous solution at 25 °C.

Answer in brief

Using the limiting law with A = 0.509, γ±(NaCl) = 0.889 and γ±(Na₂SO₄) = 0.880.

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Topic notes: electrolytic conductance, Kohlrausch's law, transport numbers and the Debye–Hückel limiting law, with every Civil Services, IFoS and Geo-Scientist PYQ →

CoversDebye-Hückel limiting lawmean ionic activity coefficientionic strengthNaClNa2SO4

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