In the fractional precipitation pictured in Figure 18-4 and described in Example 18-7, no mention was made of the concentration of the AgNO₃(aq) used. Is this concentration immaterial? Explain.

Figure 18-4

Example 18-7

AgNO₃(aq) is slowly added to a solution that has [CrO₄^2-] = 0.010 M and [Br^-] = 0.010 M.

(a) Show that AgBr(s) should precipitate before Ag₂CrO₄(s) does.

(b) When Ag₂CrO₄(s) begins to precipitate, what is [Br^-] remaining in solution?

(c) Is complete separation of Br^-(aq) and CrO₄^2-(aq) by fractional precipitation feasible?

Transcribed Image Text:

-AgNO3 solution- [CrO₂2] = [Br] = 0.010 M 10 (b) [Ag+] 1.0 x 10-5 M [CrO2] = 0.010 M [Br] 5.0 x 10-8 M AgBr(s)