The solubility product constant of Ag2CrO4 and AgBr are 1.1 × 10–12 and 5.0 × 10–13 respectively. Calculate the ratio of the molarities of their saturated solutions.

Given:

Ksp of Ag2CrO4 =1.1 × 10–12


Ksp of AgBr = 5.0 × 10–13


To find the ratio of molarities of Ag2CrO4 and AgBr saturated solutions, first, we will calculate their solubilities separately and then calculate the ratio. Hence,


Ionization of Ag2CrO4:


Ag2CrO4 2Ag+ + CrO42-


As we know that,


Ksp = [A+] [B-]


Where A and B are the ions dissolved


In the above reaction:


[A+] = [Ag+]


[B-] = [CrO42-]


Ksp = [Ag+]2 + [CrO42-]


As Ksp of Ag2CrO4 =1.1 × 10–12


Let ‘s’ be the solubility of Ag2CrO4


[Ag+] =2s


[CrO42-] =s


1.1 × 10–12 = (2s)2(s)


1.1 × 10–12 = (4s)3


s =


s = 6.5× 10-5


Ionization of AgBr:


AgBr Ag+ + Br-


As we know that,


Ksp = [A+] [B-]


Where A and B are the ions dissolved


In the above reaction,


[A+] = [Ag+]


[B-] = [Br-]


Ksp = [Ag+] + [Br-]


As Ksp of AgBr =5.0 × 10–13


Let s’ be the solubility of AgBr


5.0 × 10–13 = (s)(s)


1.1 × 10–12 = (s)2


s =


s’ = 7.07× 10-7


Now the ratio of their solubilities


= = 9.91


Thus, the ratio of molarities of their saturated solutions is 9.91


68