6.2 Forming and dissolving of precipitates -6.2.1 The solubility product rule -6.2.2 The common ion effect and salt effect 6.2.3 The effect of pH on solubility -6.2.4 The effect of complex ions formation on solubility
§ 6.2 Forming and dissolving of precipitates 6.2.4 The effect of complex ions formation on solubility 6.2.3 The effect of pH on solubility 6.2.2 The common ion effect and salt effect 6.2.1 The solubility product rule
6.2.1 The solubility product rule A B(s)-nA"(aq)+mB"(aq) J={c(Am+)}"{c(B"-)}m The solubility product rule:The reaction quotient criterion for precipitationsolubility equilibria Jp,equilibrium proceeds in reverse direction ☆J=Kp°，equilibrium state,.saturated solution ☆J<Kp°，equilibrium proceeds in forward direction
6.2.1 The solubility product rule mnnm )}(B{)}A({ + − = ccJ BA (s) nA (aq) mB (aq) m n mn + − + The solubility product rule: The reaction quotient criterion for precipitation—solubility equilibria ☆ J >Ksp Θ , equilibrium proceeds in reverse direction ☆ J = Ksp Θ , equilibrium state, saturated solution ☆ J < Ksp Θ , equilibrium proceeds in forward direction
5×10-5 J>K0 3X10-3 Solid 1X10-5 JKK -K Solutio 0 1×10-3 3×10-3 5X10-5 c(Cro)/(mol.L-1) PbCrOa(s)
PbCrO4(s) Solid Solution c(CrO4-) / (mol.L-1)
Application of the solubility product rule Example:BaCO(s)-Ba2(aq)+C (aq) ①Adding acids:2H+CO}→H2O+CO: c(CO?)↓J↓J<K Adding acids is beneficial to dissolving BaCO, 2Adding BaCl2 or Na2CO3 c(Ba2+)个orc(CO3)个J个J>K9 BaCO;will precipitate out
Example： 2 2 2 CO2H 3 ⎯+ ⎯→ +COOH + − BaCO3 will precipitate out. ② Adding BaCl2 or Na2CO3 ① Adding acids: BaCO (s) Ba (aq) CO (aq) 23 2 3 + − + Adding acids is beneficial to dissolving BaCO3 2 3 c )(CO JJ < ↓↓ − Ksp or 23 c )(CO JJ > ↑↑ − ↑ + )(Ba 2 c Ksp Application of the solubility product rule
Example:Supposing 10.0L of 0.010mol-L-1 BaCl,is added to 40.0L of a solution that contains SO2 ion with a concentration of6.0×104 mol-L-1 at25℃. Does BaSOa precipitate?If so,how many grams of BaSO are formed?What is the concentration of SO2- in the final solution? K9=1.1×100 Answer: c(S0)= 6.0×10-4×40.0 =4.8×104mol.L 50.0 c(Ba2+)= 0.010×10.0 =2.0×103mol.L 50.0
Example：Supposing 10.0L of 0.010mol·L-1 BaCl2 is added to 40.0L of a solution that contains SO42- ion with a concentration of 6. 0×10-4 mol·L-1 at 25℃. Does BaSO4 precipitate? If so, how many grams of BaSO4 are formed? What is the concentration of SO42- in the final solution? Answer: 4 1 4 2 4o Lmol108.4 0.50 0.40100.6 )SO( − − − − ⋅×= ×× c = 2 3 1 o Lmol100.2 0.50 0.10010.0 )Ba( + − − ⋅×= × c = 10 sp 101.1 − K ×=