Ionic vs. Covalent

Question

I am doing a lab where I need to determine if a substance is ionic or covalent. I have done a conductivity test and a melting point test, but my results were not conclusive. When the substance was dissolved in water it conducted electricity, but it had a melting point around 80 degrees celsius. The substance also had a 13.5 on the pH scale and had little to no smell.

Is there any other tests I could do to determine if this substance is ionic or covalent?

Answer 1

If it conducts electricity, it is most likely ionic, but there are many covalent compounds that will conduct a current, just not as well as ionic compounds (compare strong and weak electrolytes). The low melting point is more in keeping with a covalent compound. So, one can see your dilemma. There really aren't any definitive tests that you can use to tell one from the other. Conductivity and melting points are the general approach. Are you certain that the compound is pure? Are you sure your data on both conductivity and melting point are reliable? About the only thing you can say is that the unknown is soluble in water (polar) and is a base (pH > 7).