Question

1. You have a mixture of three soluble cations with the following concentrations:

   i. Ag⁺ with [Ag⁺] = 0.02 M

   ii. Ca²⁺ with [Ca²⁺] = 0.1 M and

   iii. Ba²⁺ with [Ba²⁺] = 0.1 M

   Assuming that you are slowly adding CrO4^2- ions, which ion will precipitate first, second and third? The following K_sp values are provided.

   K_sp of Ag₂CrO₄ is 1.9 × 10^-12

   K_sp of CaCrO₄ is 7.1 × 10^-4

   K_sp of BaCrO₄ is 1.2 × 10^-10

   	1.	Ag+ first, Ca2+ second, and Ba2+ last
   	2.	Ag+ first, Ba2+ second, and Ca2+ last
   	3.	Ba2+ first, Ag+ second, and Ca2+ last
   	4.	Ba2+ first, Ca2+ second, and Ag+ last

Answer 1

0200 Determine [er Op 20 needed to start precipulate 03.00 Aggero 2 Ag+ Cro 20 Baeroa = Ba2O + Cro 20 - Ksp [Ago] x [ero 20 ksp 2 [Ba 20 [oro 2 04.00 ) [ero 20 = 1.9 x 1012 = 1.281010 0.1 klero, 20 (0.02)2 = [ero, 20 1.2 x 10 9 - 4.75 x 10-9 Ca Croa a 2 + Crog 20 Ksp = [Ca 20] [ero, 20] 07.00 2 [er0 20 = 7.1x154 7.14 103 0.1 05.00 Eve. So for Balroq it needs least amount of [oroa 20 Hence option ② is correct. First B. 20 second A Last Ca2 OG NOTES: