Heterogeneous equilibria and calcite solubility. If river water in Box 7-2 is saturated with calcite (CaCO₃), [Ca²⁺] is governed by the following equilibria:

(a) From these reactions, find the equilibrium constant for the reaction

(b) The mass balance for Reaction A is [HC₃^-] = 2[Ca²⁺]. Find [Ca²⁺] (in mol/L and in mg/L) in equilibrium with atmospheric CO₂ if PCO2 = 3.8 × 10^-4bar. Locate this point on the line in Box 7-2.

(c) The concentration of Ca²⁺ in the Don River is 80 mg/L. What effective PCO₂ is in equilibrium with this much Ca²⁺? How can the river have this much CO₂?

Transcribed Image Text:

К.р — 4.5 X 10 9 Ksp Ксо, 3D 0.032 CACO3(s) = Ca2+ + CO?- CO2(8) = CO2(aq) CO,(aq) + H20 = HCO, + H* К, %3D 4.46 X 10 7 HCO, = CO + H* K2 = 4.69 x 10-11