Question

If a solution containing 0.10 M Cl-, Br-, I-, and LaTeX: CrO_4^2-C r O 4 2 − is treated with Ag+, in what order will the anions precipitate? From first to last: (Ksp of AgCl: 1.8e-10, Ksp of AgBr: 5.0e-13, Ksp of AgI: 8.3e-17, Ksp of LaTeX: Ag_2CrO_4A g 2 C r O 4: 1.2e-12)

Answer 1

The anions in a solution containing 0.10 M Cl-, Br-, I-, and CrO42- will precipitate when treated with Ag+ in the order: AgI, AgBr, Ag2CrO4, AgCl, based on their respective Ksp values.

Step-by-step explanation:

When a solution containing 0.10 M Cl-, Br-, I-, and CrO42- is treated with Ag+, the order in which the anions precipitate can be determined by comparing the product of the concentration of Ag+ needed to start precipitation and the concentration of the anion, which is given by the solubility product constant (Ksp). The anion that precipitates first is the one that forms a solid with silver at the lower concentration of Ag+.

For AgCl: The Ksp is 1.8×10-10, and AgCl begins to precipitate when [Ag+] is 1.8×10-9 M. For AgBr: The Ksp is 5.0×10-13, and AgBr begins to precipitate when [Ag+] is 5.0×10-9 M. For AgI: The Ksp is 8.3×10-17, so it precipitates at an even lower [Ag+] than AgCl and AgBr. Lastly, for Ag2CrO4: The Ksp is 1.2×10-12; it has a higher solubility than AgBr but lower than AgCl.

Based on the Ksp values and the calculations for the concentrations of Ag+ needed to start precipitation, the anions will precipitate in the following order: AgI > AgBr > Ag2CrO4 > AgCl. This order is due to the fact that AgI has the lowest Ksp (most insoluble), followed by AgBr, Ag2CrO4, and finally AgCl has the highest Ksp (most soluble).

Answer 2

`AgI \longrightarrow AgBr \longrightarrow Ag_2CrO_4 \longrightarrow AgCl`

Step-by-step explanation:

The first thing to have in mind is that the Ksp (constant of solubility) gives you an idea of how much soluble a salt is. If the concentration of ions of that salt exceeds the kps, the salt will precipitate.

The Kps of all these salts are very small compared to the 0.1 M concentration of the anions so all of them will precipitate.

The smaller the constant, the faster the salt precipitates

Having that concept in mind, the order of precipitation from first to last would be:

`AgI \longrightarrow AgBr \longrightarrow Ag_2CrO_4 \longrightarrow AgCl`