Which of the following salt solutions has `pH lt7` ? .

Options

A. `NH_(4)F`
B. `Cr(NO_(3))_(3)`
C. `[(CN_(3))_(3)overset(o+)NH]CI^(Theta)`
D. `CaI_(2)`

Answer

A, B, C

Explanation

Salt of `W_(B)//S_(A)` have `pH gt 7`.
Note: salt of `W_(A)//S_(B)` have `pH lt 7` if acidic part is stronger i.e., if `pK_(b) gt pK_(a)`.
a. `{:(NH_(4)F ,-= NH_(3),+ HF,,(K_(a)gtK_(b)orpK_(b)gtpK_(a))),(,W_(B),W_(A),,(pHlt7)):}`
b. `{:(Cr(NO_(3))_(3)-=,Cr(OH)_(3)+,HNO_(3)[pHlt7]),(,W_(B),S_(A)):}`
c. `{:([(CH_(3))_(3)NH]CI-=(CH_(3))_(3),overset(o+)NHoverset(Theta)OH+,HCI,(pHgt7)),(,W_(B),S_(A),):}`
d. `{:(CaI_(2)-=,Ca(OH)_(2)+,HI(pH=7),),(,S_(B),S_(A),):}`