Question

Which of the following is a base according to Lowry-Bronsted concept?

• A. ${\mathrm{NH}}_4^{+}$
• B. ${\mathrm{I}}^{-}$
• C. $\mathrm{HCl}$
• D. ${\mathrm{H}}_3{\mathrm{O}}^{+}$

Answer 1

The correct option is B

${\mathrm{I}}^{-}$

Explanation for the correct option

B. ${\mathrm{I}}^{-}$

• Lowry-Bronsted theory: According to this theory, an acid is a substance that can donate a proton (${\mathrm{H}}^{+}$) and a base is a substance that has the tendency to accept a proton.
• Iodide ion (${\mathrm{I}}^{-}$) can accept a proton to form its conjugate acid, hydroiodic acid ($\mathrm{HI}$).
• $$\begin{gathered} {\mathrm{I}}^{-}\left(\mathrm{aq}\right)+{\mathrm{H}}^{+}\left(\mathrm{aq}\right)\to \mathrm{HI}\left(\mathrm{aq}\right) \\ \mathrm{Iodide}\mathrm{ion}\mathrm{Hydrogen}\mathrm{ion}\mathrm{Hydroiodic}\mathrm{acid} \end{gathered}$$
• Thus, ${\mathrm{I}}^{-}$ is a base according to the Lowry-Bronsted concept.

Explanation for the incorrect options:

A. Ammonium ion (${\mathrm{NH}}_4^{+}$) can donate a proton to form ammonia (${\mathrm{NH}}_3$). Thus, it is an acid according to the Lowry-Bronsted concept.

C. Hydrochloric acid ($\mathrm{HCl}$) can donate a proton. Thus, it is an acid according to the Lowry-Bronsted concept.

D. Hydronium ion (${\mathrm{H}}_3{\mathrm{O}}^{+}$) can donate a proton to form water (${\mathrm{H}}_2\mathrm{O}$). Thus, it is an acid according to the Lowry-Bronsted concept.

Hence, the correct option is B.