Question

Which of the following salt solution has pH < 7?

• A. $N{H}_{4}F$
• B. $Cr(N{O}_3{)}_3$
• C. $\left[\right(C{H}_3{)}_{3}N{H}^{+}]C{l}^{-}$
• D. $Ca{I}_2$

Answer 1

Answer: (B), (C)

The correct options are
B

$Cr(N{O}_3{)}_3$

C

$\left[\right(C{H}_3{)}_{3}N{H}^{+}]C{l}^{-}$

Salt of weak base(WB) + strong acid (SA) have pH < 7

$A)N{H}_{4}F\to \underset{WB}{N{H}_3}+\underset{WA}{HF}(K_a>K_{b}orp{K}_b>p{K}_{a}hencepH>7)$

$B\left)Cr\right(N{O}_3{)}_3\to \underset{WB}{Cr(OH{)}_3}+\underset{SA}{HN{O}_3}$
$C\left)\right[\left(C{H}_3{)}_{3}N{H}^{+}\right]C{l}^{-}\to \underset{WB}{(C{H}_3{)}_{3}N{H}^{+}O{H}^{-}}+\underset{S.A}{HCl}$
$D)Ca{I}_2\to \underset{SB}{Ca(OH{)}_2}+\underset{SA}{HI}$