Govt Exams
E°cell is directly related to the maximum electrical work (w_max = -nFE°cell) that can be obtained from a galvanic cell.
Hydration enthalpy depends on the charge density of the ion (charge/size ratio). Higher charge and smaller size lead to greater hydration enthalpy.
If 30% of PCl₅ dissociates, [PCl₃] = 1 × 0.30 = 0.3 M and [Cl₂] = 0.3 M.
Using ln(k₂/k₁) = (Ea/R)(T₂-T₁)/(T₁T₂), ln(2) = (Ea/8.314)(10)/(93000). Solving: Ea ≈ 52.8 kJ/mol.
ΔG° = -nFE°, so E° = -ΔG°/(nF) = 95500/(2 × 96500) = 0.495 V
α = √(Ka/C) = √(4×10⁻⁶/0.1) = √(4×10⁻⁵) = 0.0063 or 0.63%
At phase transition equilibrium, ΔG° = ΔH° - TΔS° = 0 because the process is reversible
Initial: PCl₅ = 1 atm. At equilibrium with α = 0.4: PCl₅ = 0.6, PCl₃ = 0.4, Cl₂ = 0.4 atm. Kp = (0.4 × 0.4)/(0.6) = 0.267 atm
Born-Landé equation specifically calculates lattice energy of ionic compounds based on ionic radii and charges
In compression, volume decreases and work is done ON the gas, making w positive (in physics convention). W = -nRT ln(Vf/Vi) where Vf < Vi