Question

a student wants to determine whether an unknown solid is an ionic compound. he puts some in water and finds that it does not dissolve. he says that this proves the solid is ionic. which best evaluates the students reasoning? he is incorrect, because water can dissolve ionic solids. the test proves nothing, because water dissolves all solids. he is correct, because polar liquids cannot dissolve ionic solids. the test proves nothing, because it only shows that the solid is a compound.

Explanation:

Ionic compounds can dissolve in water due to the attraction between water molecules and the ions in the compound. Just because a solid doesn't dissolve in water doesn't prove it's ionic as there are many non - ionic solids that also don't dissolve in water. Water does not dissolve all solids. Also, polar liquids like water can dissolve many ionic solids. The fact that the solid doesn't dissolve only tells us it's insoluble in water, not that it's ionic.

Answer:

He is incorrect, because water can dissolve ionic solids.