Question

Which of the following ions does not liberate hydrogen gas on reaction with dilute acids?

• A. ${Ti^{2+}}$
• B. ${V^{2+}}$
• C. ${Cr^{2+}}$
• D. ${Mn^{2+}}$

Answer 1

Answer: (D)

${Mn^{2+}}$

Answer 2

These elements belong to the transition metal series, and their reactivity diminishes sequentially as we progress from $Ti^{2+}$ to $V^{2+}$ to $Cr^{2+}$ and finally to $Mn^{2+}$ across the fourth row of the periodic table. Consequently, $Mn^{2+}$ does not release hydrogen gas when reacting with dilute acids.

So, the correct option is (D): ${Mn^{2+}}$