Question

Of the following complex ions, one is a Bronsted-lowry acid. That one is:

• A. ${\left[Cu{\left(N{H}_3\right)}_4\right]}^{2+}$
• B. ${\left[Fe{Cl}_4\right]}^{-}$
• C. ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$
• D. ${\left[Zn{\left(OH\right)}_4\right]}^{2-}$

Answer 1

The correct option is C ${\left[Fe{\left(H_{2}O\right)}_6\right]}^{3+}$

A Bronsted Lowry acid is defined simply as a proton donor.

Out of all the four complex ions, the only one that can donate a proton is the $\text{hexa aquairon (III)}$ ion $\left[Fe\right(H_{2}O{)}_6{]}^{3+}$.

$\left[Fe\right(H_{2}O{)}_6{]}_{\left(aq\right)}^{3+}+{H_{2}O}_{\left(l\right)}\rightleftharpoons \left[Fe\right(H_{2}O{)}_5\left(OH\right){]}^{2+}+{H_{3}O}_{\left(aq\right)}^{+}$