Final answer:
The calcium ion (Ca²⁺) is the most likely to form an insoluble sulfate according to solubility rules.
Step-by-step explanation:
The student asked which of the following ions is most likely to form an insoluble sulfate? The options provided were A) K⁺ B) Li⁺ C) Ca²⁺ D) S²⁵ E) C¹⁵.
According to solubility rules, sulfates (SO4²⁵) are generally soluble except when paired with certain divalent cations such as Ca²⁺ (calcium), Sr²⁺ (strontium), and Ba²⁺ (barium).
Thus, the calcium ion (Ca²⁺) is the most likely to form an insoluble sulfate.
The ion most likely to form an insoluble sulfate is Ca²+. According to the solubility rules, sulfates (SO²-) are generally soluble except when they are formed with calcium (Ca²+), strontium (Sr²+), and barium (Ba²+).
These divalent cations form insoluble sulfates. Therefore, among the given options, Ca²+ is the ion most likely to form an insoluble sulfate.