Solubility Equilibria Chapter 15

Objectives Define key terms and concepts Calculate the solubility product for a compound. Calculate concentration and solubility using the common ion and complex ion effects. Develop and utilize a flow chart for use in qualitative analysis.

Solubility Equilibria Solubility Product (Ksp) The product of the molar concentrations of the ions that make-up a compound, each raised to the power of it’s stoichiometric coefficient. The smaller the Ksp value, the less soluble the compound is in water. BaCO3 ↔ Ba2+ + CO32- Ksp = [Ba2+] [CO32-] BaF2 ↔ Ba2+ + 2F- Ksp = [Ba2+] [F-]2

Solubility Equilibria The saturation level of a solution can be determined using Ksp and Q. If Q < Ksp, the solution is unsaturated If Q > Ksp, the solution is supersaturated If Q = Ksp, the solution is saturated

Write the solubility product expression for the following salts: AgCl Hg2Cl2 Pb3(AsO4)2

A liter of a solution saturated at 25°C with calcium oxalate, CaC2O4, is evaporated to dryness, giving a 0.0061g residue of CaC2O4. Calculate the solubility product constant for the salt at 25°C.

By experiment, it is found that 1 By experiment, it is found that 1.2x10-3mole of lead (II) iodide dissolves in 1L of aqueous solution at 25°C. What is the solubility product constant at this temperature?

Solubility Equilibria Molar Solubility The number of moles of solute in 1 liter of saturated solution Moles per liter Solubility The number of grams of solute in 1 liter of saturates solution Grams per liter These both refer to solutions at a specific temperature

Solubility Product and Molar Solubility

Calculate the solubility in g/L of lead (II) chromate in water Calculate the solubility in g/L of lead (II) chromate in water. The Ksp for PbCrO4 is 1.8x10-14.

Calculate the solubility in g/L for lead (II) arsenate when dissolved in water. The Ksp for Pb3AsO4)2 is 4.0x10-36.

Calculate the solubility product for potassium nitrate if the solubility of the compound in water is 133g/L at 0°C.

If 0.17g of calcium fluoride is soluble in 1L of solvent, what is the solubility product of calcium fluoride?

Precipitation Reactions If the ion product exceeds the Ksp, a precipitate will form. Soluble Compounds Almost all salts of Na+, K+, and NH4+ Salts of NO3-, ClO3-, ClO4-, C2H3O2- Exceptions Almost all salts of Cl-, Br-, I- Halides of Ag+, Hg2+, Pb2+ Compounds containing F- Fluorides of Mg2+, Ca2+, Sr2+, Ba2+, and Pb2+ Salts of SO42- Sulfates of Ca2+, Sr2+, Ba2+, Pb2+ Insoluble Compounds Most salts of CO32-, PO43-, C2O42-, CrO42- Salts of NH4+ and alkali metal cations Most metal sulfides, S2- Most metal hydroxides and oxides

Common Ion Effect and Solubility A compound can be precipitated out of solution if another compound containing a common ion is added to the solution. The saturation level of a solution can be determined using Ksp and Q (ion product). If Q < Ksp, the solution is unsaturated If Q > Ksp, the solution is supersaturated If Q = Ksp, the solution is saturated

Common Ion Effect and Solubility

Which of the following compounds should most affect the solubility of lead (II) sulfate in water to which it has been added? a) NaCl b) Na2SO4 c) PbS Which of the following compounds should most affect the solubility of silver chloride in water to which it has been added?

The concentration of calcium ion in blood plasma is 0. 0025M The concentration of calcium ion in blood plasma is 0.0025M. If the concentration of oxalate ion is 1.0x10-7M, do you expect calcium oxalate to precipitate? Ksp for calcium oxalate is 2.3x10-9.

AgCl will be dissolved into a solution with is ALREADY 0 AgCl will be dissolved into a solution with is ALREADY 0.0100 M in chloride ion. What is the solubility of AgCl? The  Ksp =1.77 x 10¯10

What is the solubility of Ca(OH)2 in 0. 0860 M Ba(OH)2 What is the solubility of Ca(OH)2 in 0.0860 M Ba(OH)2? The Ksp for Ca(OH)2 is known to be 4.68 x 10¯6.

Will silver chloride precipitate from a solution that is 0 Will silver chloride precipitate from a solution that is 0.01M AgNO3 and 0.01M NaCl? The Ksp for silver chloride is 8.3x10-17

Will silver iodide precipitate from a solution that is 0 Will silver iodide precipitate from a solution that is 0.0045M AgNO3 and 0.15M NaI? The Ksp for silver iodide is 1.8x10-10.

Sulfate ion in solution is often determined quantitatively by precipitating it as barium sulfate. The sulfite ion may have been formed from a sulfur compound. Analysis for the amount of sulfate ion then indicates the percentage of sulfur in the compound. Is a precipitate expected to form at equilibrium when 50mL of 0.0010M barium chloride is added to 50mL of 0.00010M sodium sulfate? The solubility product constant for barium sulfate is 1.1x10-10.

If 1.1 x 10-4 g of Cr(OH)3 is added to 120 L of water at 25 °C, will all of the solute dissolve? The of chromium (III) hydroxide is Ksp = 6.7 x 10-31. If 4.0 x 10-4 g of NaOH is added to the solution described above, will a precipitate form? Calculate the molar solubility of Cr(OH)3 in a solution buffered at pH = 11.00.

Complex Ion Equilibria and Solubility An ion containing a central metal cation bonded to one or more molecules or ion. Commonly formed by transition metals Formation Constant (Kf) The equilibrium constant for complex ion formation The larger the Kf, the more stable the complex

Complex Ions

Complex Ions

Complex Ions

Complex Ions Cu2+ + 4NH32+  Cu(NH3)42+ (solutions turns a deep blue) Ni2+ + 6NH3  Ni(NH3)62+ (Solutions is blue)

Calculate the silver ion concentration, [Ag+], of a solution prepared by dissolving 1.00g of silver nitrate and 10.0g of potassium cyanide in 1.00 of solution.

Calculate the [HgCl42-] in a solution prepared by adding 0 Calculate the [HgCl42-] in a solution prepared by adding 0.0200M of NaCl to 0.250L of a 0.100M HgCl2 solution.

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