UPSC Combined Geo-Scientist, Mains · 2016 · Mains Paper III

Q1(j). Solubility product from potentials

Question

Given E°(AgBr/Ag,Br⁻)=0.071 V and E°(Ag+/Ag)=0.799 V, calculate Kₛₚ of AgBr.

Kₛₚ≈4.95×10⁻¹³ at 298 K.

Subtract the silver reduction from the silver bromide reduction to obtain AgBr(s) → Ag⁺ + Br⁻.
For this combined reaction ΔG°=F(0.799-0.071)=0.728F.
Since ΔG°=-RTln Kₛₚ, log Kₛₚ=-0.728/0.05916=-12.3056. Pure solids have unit activity.

The full model answer

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