Silver nitrate (AgNO₃)is slowly added to a solution containing 0.100 M Br− and 0.050 M FeCN₆⁴⁻ until a precipitate just forms.What is the molar concentration of Ag⁺ just as the precipitate forms? AgBr K_sp = 5.0 × 10^-13 and Ag₄FeCN₆ K_sp = 8.5 × 10^-45. A)2.0 × 10^-11 M Ag⁺ B)5.0 × 10^-12 M Ag⁺ C)1.0 × 10^-11 M Ag⁺ D)3.3 × 10^-12 M Ag⁺ E)1.7 × 10^-43 M Ag⁺

Question

Quizplus · Accepted Answer

The balanced chemical equation for the reaction is: AgNO3 + NaBr + Fe(CN)6 --> AgBr + NaNO3 + Fe(CN)6 The limiting reactant in this reaction is NaBr, as it is present in lower concentration. Using the stoichiometry of the balanced equation, the concentration of Ag+ at precipitation can be calculated as follows: 5.0 x 10^-13 = [Ag+][Br-] / [AgBr] [Ag+] = (5.0 x 10^-13) x (0.100) / 5.0 x 10^-1 = 1.0 x 10^-12 M Similarly, the concentration of Ag+ with Fe(CN)6 can be calculated using the same method: 8.5 x 10^-45 = [Ag+][Fe(CN)6-4] / [AgFe(CN)6] [Ag+] = (8.5 x 10^-45) x (0.050) / 8.5 x 10^-10 = 5.0 x 10^-16 M As Ag+ is consumed completely in the reaction with Br-, the lower value of [Ag+] is the correct concentration just before the precipitate forms. Therefore, the molar concentration of Ag+ and AgBr at precipitation is 5.0 × 10^-12 M. Since the stoichiometry of the balanced equation indicates that one Ag+ ion reacts with one Br- ion to form one AgBr precipitate, the concentration of Ag+ and AgBr is equal to the concentration of Ag⁺. Hence, the answer is B.

Silver Nitrate (AgNO3)is Slowly Added to a Solution Containing 0

Silver Nitrate (AgNO₃)is Slowly Added to a Solution Containing 0