When a base is dissolved in a solution, the type of ion that is formed is determined by the chemical properties of bases. A base is a substance that can accept protons (H⁺ ions) or donate a pair of valence electrons to form a bond. The process of dissolution of a base typically releases hydroxide ions (OH⁻) into the solution.
To answer the question, we need to identify which of the given ions corresponds to the species commonly formed when a base dissociates in water:
1. [tex]\( \text{H}^+ \)[/tex]: This represents a proton or hydrogen ion, which is typically associated with acids, not bases.
2. [tex]\( \text{O}^- \)[/tex]: This is an oxygen anion with a single negative charge, which is not commonly associated with the dissolution of bases in water.
3. [tex]\( \text{OH}^- \)[/tex]: This represents the hydroxide ion, which is characteristically formed when a base dissolves in water.
4. [tex]\( \text{SO}_4^{2+} \)[/tex]: This represents a sulfate cation with a double positive charge, which is not related to the behavior of bases dissolving in water.
Therefore, when a base is dissolved in a solution, the ion that is formed is:
[tex]\[ \text{OH}^- \][/tex]
So, the correct answer is:
[tex]\[ \text{OH}^- \][/tex]
