A beaker contains a solution that is 0.50 M in Au+3 ion and 0.25 M in Ag+ ion. A soultion of sodium chloride is slowly dripped into the beaker with stirring. Which ion will precipitate first, the gold or the silver? Clearly support your answer and write out your final conclusion in an explanatory sentence.

Question

A beaker contains a solution that is 0.50 M in Au+3 ion and 0.25 M in Ag+ ion. A soultion of sodium chloride is slowly dripped into the beaker with stirring. Which ion will precipitate first, the gold or the silver? Clearly support your answer and write out your final conclusion in an explanatory sentence. 
Ksp for AuCl3 = 3.2 x 10^-25 
Ksp for AgCl = 1.8 × 10^-10

DrBob222 · Answer

I'll give you some hints but it is up to you to put all of it together to make a coherent answer.
For AuCl3 ==> Ag^3+ + 3Cl^-
Write out Ksp expression and solve for (Cl^-). Plug in Ksp, (Au^3+) = 0.5M and calculate (Cl^-)

Do the same for AgCl
AgCl --> Ag^+ + Cl^-
Write out the Ksp expression, plug in Ksp and 0.25 for (Ag^+) and solve for (Cl^-).
So if you have those ions in solution and you need (Cl^-) to be what you have calculated above. which will ppt first? Of course the one that requires the smallest Cl^-. Identify that and put all of the equations and math in good order and you'll get an A+ on the assignment.