Q1(e). Solubility product of silver chromate

Answer in brief

Ksp (Ag₂CrO₄) = 1.71 × 10⁻¹² mol³ L⁻³.

Key points

• Ag₂CrO₄(s) ⇌ 2Ag⁺ + CrO₄²⁻; at saturation [Ag⁺] = 2s, [CrO₄²⁻] = s.
• Molar solubility s = 2.5 × 10⁻² / 331.728 = 7.536 × 10⁻⁵ mol L⁻¹.
• Ksp = [Ag⁺]²[CrO₄²⁻] = (2s)²(s) = 4s³ = 4 × 4.280 × 10⁻¹³ = 1.71 × 10⁻¹².
• This low Ksp is used in Mohr’s method: red Ag₂CrO₄ appears only after AgCl is complete.