MY and `NY_(3)` two nearly insoluble salts, have the same `K_(sp)` values of `6.2xx10^(-13)` at room temperature. Which statement would be true in rearged to MY and `NY_(3)` ?

Options

A. The addition of the salt of KY to the solution of MY and `NY_(3)` will have no effect on their solubilities
B. The molar solubilities of MY and `NY_(3)` in water are identical
C. The molar solubility of MY in water is less than that of `NY_(3)`
D. The salts MY and `NY_(3)` are more soluble in 0.5 M KY than in pure water .

Answer

C

Explanation

`{:(MY,hArr,M^(+),+ ,Y^(-)),(S,,S,,S):}`
`K_(sp)=[M^(+)][Y^(-)]=S_(1).S_(1)=S_(1)^(2)`
or `S_(1)=sqrt(K_(sp))=7.87xx10^(-7) "mol" L^(-1)`
`{:(NY_(3),hArr,N^(+),+ ,3Y^(-)),(S_(2),,S_(2),,3S_(2)):}`
`K_(sp)=[N^(3+)][Y^(-)]^(3)=S_(2)(3S_(2))^(3)=27S_(2)^(4)`
or `S_(2)=((K_(sp))/(27))^(1//4)=((6.2xx10^(-13))/(27))^(1//4)`
`=3.89xx10^(-4)" mol" L^(-1)`
Evidently , `S_(1) lt S_(2)`