**Question 12**The following pictures represent solutions at various stages in the titration of a weak diprotic acid \( \text{H}_2\text{A} \) with aqueous KOH. Unshaded spheres represent H atoms, black spheres represent oxygen atoms, and shaded spheres represent \( \text{A}^{2-} \) ions. (\( \text{K}^+ \), \( \text{H}_3\text{O}^+ \) initially present, \( \text{OH}^- \) initially present and solvent water molecules have been omitted for clarity.)**Diagram Explanation:**1. **Picture (1):** Contains only molecules of the form \( \text{H}_2\text{A} \).2. **Picture (2):** Contains a mix of \( \text{H}_2\text{A} \) and \( \text{HA}^- \) ions.3. **Picture (3):** Contains a mix of \( \text{HA}^- \) and \( \text{A}^{2-} \) ions.4. **Picture (4):** Contains only \( \text{A}^{2-} \) ions.*Which picture represents the system halfway to the first equivalence point?*- (1)- (2)- (3)- (4)*Instructions: Click Save and Submit to save and submit. Click Save All Answers to save all answers.*

By definition, An equivalence point is the point in the titration at which all of the acid has been consumed completely. Therefore, halfway of the equivalence point will be the point exactly half of the acid has been consumed. So, at halfway of the first equivalence point in the given titration, the amount of species present are: H2A = HA- Also, there will be no A2- in the reaction mixture at this point because A2- is formed only after the first equivalence point has been crossed. In a titration, base is added dropwise to the acid. So, no OH- will be there in the reaction mixture at this point.Therefore, at halfway of the first equivalence point, the species present are H2A and HA- in equal amounts. So, the correct answer is: 3 molecules each of H2A and HA- are present.