To determine the number of ions that can liberate hydrogen from a dilute acid, we need to analyze their reducing abilities. Strong reducing agents can donate electrons to \(\text{H}^+\), reducing it to \(\text{H}_2\).
Step 1: Evaluate \(\text{Ti}^{2+}\)
Titanium(II) (\(\text{Ti}^{2+}\)) has a strong tendency to get oxidized to \(\text{Ti}^{3+}\), making it a strong reducing agent.
\(\text{Ti}^{2+}\) can react with \(\text{H}^+\) from dilute acids to liberate \(\text{H}_2\).
Step 2: Evaluate \(\text{Cr}^{2+}\)
Chromium(II) (\(\text{Cr}^{2+}\)) is a strong reducing agent and can be oxidized to \(\text{Cr}^{3+}\).
\(\text{Cr}^{2+}\) reacts with \(\text{H}^+\) from dilute acids to liberate \(\text{H}_2\):
\[2\text{Cr}^{2+} (\text{aq}) + 2\text{H}^+ (\text{aq}) \rightarrow 2\text{Cr}^{3+} (\text{aq}) + \text{H}_2 (\text{g}).\]
Step 3: Evaluate \(\text{V}^{2+}\)
Vanadium(II) (\(\text{V}^{2+}\)) is also a strong reducing agent and can be oxidized to \(\text{V}^{3+}\).
\(\text{V}^{2+}\) reacts with \(\text{H}^+\) from dilute acids to liberate \(\text{H}_2\).
Conclusion:
All three ions (\(\text{Ti}^{2+}\), \(\text{Cr}^{2+}\), and \(\text{V}^{2+}\)) can liberate \(\text{H}_2\) from dilute acids.
Final Answer: (3).
$\mathrm{KMnO}_{4}$ acts as an oxidising agent in acidic medium. ' X ' is the difference between the oxidation states of Mn in reactant and product. ' Y ' is the number of ' d ' electrons present in the brown red precipitate formed at the end of the acetate ion test with neutral ferric chloride. The value of $\mathrm{X}+\mathrm{Y}$ is _______ .
Match List-I with List-II: List-I