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Consider each of the following: a. 1.0 M hydroxide will form a precipitate with copper(II) cation but 6.0 M hydroxide will dissolve the solid. Explain using equations and K_sp and K_f arguments. b. In the preliminary test with chloride (Section 1.1) there is a note stating that excess chloride ion must be avoided. Explain.
Expert Answer
Ans 2 A
Ans 2 B
For the accuracy, the solubility of precipitate must be minimal. Minimize the solubility losses by carefully controlling the conditions under which the precipitate forms. It requires for every equilibrium reaction affecting the precipitate’s solubility.
As we add chloride ions to a solution, the solubility initially decreases. At higher concentrations of Cl–, increase the solubility . Clearly the equilibrium concentration of chloride is important if we want to determine the concentration by precipitation. In particular, we must avoid a large excess of chloride.
