18. Aqueous Equilibrium

Ca1OH22 has a Ksp of 6.5 * 10-6. (b) If 50 mL of the solution from part (a) is added to each of the beakers shown here, in which beakers, if any, will a precipitate form? In those cases where a precipitate forms, what is its identity? [Section 17.6]

The following pictures represent solutions of Ag2CrO4, which also may contain ions other than Ag+ and CrO42- that are not shown. Solution 1 is in equilibrium with solid Ag2CrO4. Will a precipitate of solid Ag2CrO4 form in solutions 2-4? Explain.

(1)

(2)

(3)

(4)

A solution of Na2SO4 is added dropwise to a solution that is 0.010 M in Ba2 +1aq2 and 0.010 M in Sr2 +1aq2. (a) What concentration of SO42 - is necessary to begin precipitation? (Neglect volume changes. BaSO4: Ksp = 1.1 * 10-10; SrSO4: Ksp = 3.2 * 10-7.)

A solution of Na2SO4 is added dropwise to a solution that is 0.010 M in Ba2 +1aq2 and 0.010 M in Sr2 +1aq2. (c) What is the concentration of SO42 - 1aq2 when the second cation begins to precipitate?

A solution of Na2SO4 is added dropwise to a solution that is 0.010 M in Ba2 +1aq2 and 0.010 M in Sr2 +1aq2. (b) Which cation precipitates first?

A solution containing sodium fluoride is mixed with one containing calcium nitrate to form a solution that is 0.015 M in NaF and 0.010 M in Ca(NO3)2. Does a precipitate form in the mixed solution? If so, identify the precipitate.

Predict whether a precipitate will form if you mix 75.0 mL of a NaOH solution with pOH = 2.58 with 125.0 mL of a 0.018 M MgCl2 solution. Identify the precipitate, if any.

A solution is 0.010 M in Ba2 + and 0.020 M in Ca2 + . b. What is the remaining concentration of the cation that precipitates first, when the other cation begins to precipitate?

A solution is 0.010 M in Ba2 + and 0.020 M in Ca2 + . a. If sodium sulfate is used to selectively precipitate one of the cations while leaving the other cation in solution, which cation will precipitate first? What minimum concentration of Na2SO4 will trigger the precipitation of the cation that precipitates first?

Fluoridation of drinking water is employed in many places to aid in the prevention of tooth decay. Typically. the Fion concentration is adjusted to about 1 ppm. Some water supplies are also 'hard'; that is, they contain certain cations such as Ca2 + that interfere with the action of soap. Consider a case where the concentration of Ca2 + is 8 ppm. Could a precipitate of CaF2 form under these conditions? (Make any necessary approximations.)

Can Fe2+ be separated from Sn2+ by bubbling H2S through a 0.3 M HCl solution that contains 0.01 M Fe2+ and 0.01 M Sn2+? A saturated solution of H2S has [H2S] ≈ 0.10 M. Values of Kspa are 6 x 10^2 for FeS andd 1 x 10^-5 for SnS.

Will FeS precipitate in a solution that is 0.10 M in Fe(NO3)2, 0.4 M in HCl, and 0.10 M in H2S? Will FeS precipitate if the pH of the solution is adjusted to pH 8 with an NH4+ - NH3 buffer? Kspa = 6 x 10^2 for FeS.

In quantitative analysis, Ag+, Hg2+, and Pb2+ are seperated from other cations by the addition of HCl. Calculate the concentration of Cl-ions required to just begin the precipitation of (a) AgCl, (b) Hg2Cl2, (c) PbCl2 in a solution hav-ing metal-ion concentrations of 0.030 M. What fraction of the Pb2+ remains in solution when the Ag+ just begins to precipitate?