Ten grams of the hypothetical ionic compounds XZ and YZ are each placed in a separate 2.0-L

Question:

Ten grams of the hypothetical ionic compounds XZ and YZ are each placed in a separate 2.0-L beaker of water. XZ completely dissolves, whereas YZ is insoluble. The energy of hydration of the Y+ ion is greater than the X+ ion. Explain this difference in solubility.