posted by Fred .
I did a lab in which I added ionic solutions to tap and distilled water and another ionic solution. Distilled water is the control because it does not react to any solutions since it doesn't contain ions. But one of the lab questions I need to answer is:
These tests cannot absolutely confirm the absence of an ion. Why?
Thank you for helping.
Before a compound precipitates, the solution must become saturated with it. If the concentration of this compound is below saturation because one of the solutions mixed is too dilute (such as contaminated distilled water), no precipitate forms.