Final answer:
Observations of the heating process, hydration behavior, and reaction with silver nitrate can all help verify the presence of potassium chloride as the residue in the crucible.
Step-by-step explanation:
To verify that the residue in your crucible after heating is potassium chloride, you would need to rely on careful observations made during the heating process and subsequent reactions. For example, if you began with a substance like solid potassium chlorate and upon heating observe it decomposing into solid KCl and oxygen gas, as the substance changes from its original form to a new residue, it gives evidence that the residue could be potassium chloride. Another observation could come from the solubility properties depicted in Figure 7.5.2, where potassium chloride demonstrates characteristic hydration in water, with the water molecules being attracted to the K+ and Cl- ions, which could be compared with the residue's behavior in water. Lastly, the formation of a white precipitate when silver nitrate is added (as in the case with test tube Z) supports the presence of chloride ions, which further suggests that the residue is potassium chloride if no other chloride salts are expected to be present.