Question 16.10: Exactly 200 mL of 0.0040 M BaCl2 are mixed with exactly 600 ...
Exactly 200 mL of 0.0040 M BaCl_{2} are mixed with exactly 600 mL of 0.0080 M K_{2}SO_{4}. Will a precipitate form?
Strategy Under what condition will an ionic compound precipitate from solution? The ions in solution are Ba^{2+}, Cl^{-}, K^{+} , and SO^{2-}_{4} . According to the solubility rules listed in Table 4.2, the only precipitate that can form is BaSO_{4}. From the information given, we can calculate [Ba^{2+}] and [SO^{2-}_{4}] because we know the number of moles of the ions in the original solutions and the volume of the combined solution. Next, we calculate the ion product Q (Q=[Ba^{2+}]_{0}[SO^{2-}_{4}]_{0}) and compare the value of Q with K_{sp} of BaSO_{4} to see if a precipitate will form—that is, if the solution is supersaturated.
Table 4.2 Solubility Rules for Common Ionic Compounds in Water at 25°C
| Soluble Compounds | Insoluble Exceptions |
| Compounds containing alkali metal ions (Li^{+} ,Na^{+} ,Rb^{+} ,Cs^{+}) and the ammonium ion (NH^{+}_{4}) |
|
| Nitrates (NO^{+}_{3}), acetates (CH_{3}COO^{-}), bicarbonates (HCO^{-}_{3}) , chlorates (ClO^{-}_{3}), and perchlorates (ClO^{-}_{4}) |
|
| Halides (Cl^{-} ,Br^{-} ,I^{-}) | Halides of Ag^{+} ,Hg^{2+}_{2} and Pb^{2+} |
| Sulfates (SO^{2-}_{4}) | Sulfates of Ag^{+} ,Ca^{2+} ,Sr^{2+} Ba^{2+} ,Hg^{2+}_{2} and Pb^{2+} |
| Insoluble Compounds | Soluble Exceptions |
| Carbonates (CO^{2-}_{3}) , phosphates (PO^{3-}_{4}) , chromates (CrO^{2-}_{4}), |
Compounds containing alkali metal ions and the ammonium ion |
| sulfides (S^{2-}) | |
| Hydroxides (OH^{-}) | Compounds containing alkali metal ions and the Ba^{2+} ion |
