Final answer:
The concentration of the cation in the new saturated solution would remain the same when the volume of water is doubled, as solubility dictates the maximum amount of the solute that can dissolve.
Step-by-step explanation:
The concentration of a cation in a saturated solution is determined by the solubility of the compound containing the cation in water. When you double the volume of water used without adding more of the solute, the amount of the solute remains the same, but now it is dissolved in a greater volume of solvent. As a result, the concentration of the cation in the new saturated solution would remain the same, because the solute is still saturating the solvent at the solute's maximum dissolvable capacity. This is an essential concept in the study of solutions and solubility.
In other words, the solubility of a substance is a property that dictates how much can dissolve in a solvent at a given temperature. If that limit is not exceeded, adding more solvent does not affect the concentration since the ratio of solute to solvent remains constant. Once saturation is reached, any additional amount of water will not change this ratio.