The ΔH of adsorption at constant amount of vapour adsorbed is called the isosteric enthalpy of adsorption, ΔₐH. The adsorption of N₂ on charcoal amounted to 0.894 cm³ (STP)/g at (0.4 atm and 200 K) an

Question

The ΔH of adsorption at constant amount of vapour adsorbed is called the isosteric enthalpy of adsorption, ΔₐH. The adsorption of N₂ on charcoal amounted to 0.894 cm³ (STP)/g at (0.4 atm and 200 K) and (at 59.2 atm and T K). If ΔₐH = –16.628 kJ/mol, then the value of T is

Prashant Kotian · Accepted Answer

Correct answer: 0400. The Clausius-Clapeyron equation for an isostere gives ln(P₂/P₁) = (-ΔₐH/R) (1/T₁ - 1/T₂). Here, P₁ = 0.4 atm at T₁ = 200 K, and P₂ = 59.2 atm at T₂ = T. ΔₐH = -16.628 kJ/mol = -16628 J/mol, and R = 8.314 J/(mol·K). ln(59.2 / 0.4) = ln(148) ≈ 5.0. 5.0 = (-(-16628)/8.314) × (1/200 - 1/T) = 2000 × (0.005 - 1/T). 0.0025 = 0.005 - 1/T, which simplifies to 1/T = 0.0025. T = 1 / 0.0025 = 400 K. Therefore, correct answer is 0400.

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