If a solution contains 0.0020 mol of CrO2−4 per liter and solid AgNO3 is added, what concentration of Ag+ ion must be reached to cause Ag2CrO4 to begin to precipitate? For Ag2CrO4, Ksp=9.0×10−12.

Question

If a solution contains 0.0020 mol of CrO2−4 per liter and solid AgNO3 is added, what concentration of Ag+ ion must be reached to cause Ag2CrO4 to begin to precipitate? For Ag2CrO4, Ksp=9.0×10−12.

Answer 1

Ag₂CrO₄(s) ===> 2Ag⁺(aq) + CrO₄²⁺(aq)

Ksp = 9x10^-12 = [Ag⁺]²[CrO₄^2-]

9x10^-12 = (x)²(0.002)

x² = 4.5x10^-9

x = 6.5x10^-5 M = [Ag⁺]