JEE Main 2024 — D And F Block Elements Question with Solution

To determine the ability of the ions to liberate hydrogen from a dilute acid, we need to understand the standard electrode potentials of these ions in comparison to hydrogen. The standard electrode potential of hydrogen ($${\mathrm{H}}^{+}/{\mathrm{H}}_2$$) is set at 0 volts. Any metal ion with a negative standard reduction potential compared to hydrogen has the ability to liberate hydrogen gas from dilute acids because they are more likely to donate electrons to the $${\mathrm{H}}^{+}$$ ions found in acids, reducing them to $${\mathrm{H}}_2$$ gas.

The standard reduction potentials for the ions mentioned are as follows:

• $${\mathrm{Ti}}^{2+}/\mathrm{Ti}$$ is more negative than that of $${\mathrm{H}}^{+}/{\mathrm{H}}_2$$.
• $${\mathrm{Cr}}^{2+}/\mathrm{Cr}$$ also has a more negative standard reduction potential compared to $${\mathrm{H}}^{+}/{\mathrm{H}}_2$$.
• The standard reduction potential for $${\mathrm{V}}^{2+}/\mathrm{V}$$ is similarly more negative than that of $${\mathrm{H}}^{+}/{\mathrm{H}}_2$$.

Due to their negative standard reduction potentials relative to hydrogen, all three ions ($${\mathrm{Ti}}^{2+},{\mathrm{Cr}}^{2+},{\mathrm{V}}^{2+}$$) have the capacity to liberate hydrogen from a dilute acid. Therefore, the correct answer is:

Option C: 3