'11-20. In contrast to many salts, calcium sulfate is only parprecipitates first and the range of S2 concentration tially dissociated in aqueous solution: that will allow a dean separation of the two ions. CaSO4(aq)Ca2++SO42Kd=5.2103 (c) The analytical concentration of H2S in a solution saturated with H2S(g) is 0.10M. What pH range is necessary for the clean separation deseribed in part (b)? The solubility-product constant for CaSO4 is 2.6 (d) If there is no pH control from a buffer, what is 105. Calculate the solubility of CaSO4 in (a) water the pH of a saturated H2S solution? and (b) 0.0100MNa2SO4, In addition, calculate the (c) Plot the 0 and 1 values for H2S over the pH percent of undissociated CaSO4 in each solution. range of 10 to 1 . 11-21. Calculate the molar solubility of Tl2S as a function of (f) A solurion contains H2S and NH3. Four Cd2+ pH over the range of pH10 to pH 1. Find values at evcomplexes form with NH3 in a stepwise fashion: ery 0.5pH unit and use the charting function of Excel Cd(NH3)2+,Cd(NH3)22+,Cd(NH3)32+, and to plot solubility versus pH. Cd(NH3)42+. Find the molar solubility of CdS in 11-22. Challenge Problem: (a) The solubility of CdS is a solution of 0.1MNH3. normally very low, but it can be increased by lowering the solution pH. Calculate the molar (g) For the same solution components as in part ( f ), solubility of CdS as a function of pH from pH buffers are prepared with a total concentration of 11 to pH 1. Find values at every 0.5pH unit and NH3+NH4Cl=0.10M. The pH values are plot solubility versus pH. 8.0,8.5,9.0,9.5,10.0,10.5, and 11.0. Find the (b) A solution contains 1104M of both Fe2+ and molar solubility of CdS in these solutions. Cd+. Sulfide ions are slowly added to this solution to (h) For the solutions in part (g), how could you deprecipitare either FeS or CdS. Determine which ion termine whether the solubility increase with pH is duc to complex formation or to an activity effect