[Atome]

Hello everyone,

I'm not sure if I have fully answered this question. Could someone please check if my answer is correct? Thank you!

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1. A solid substance is found to be soluble in water and has a melting point of 140°C. In order to classify this solid as ionic, covalent, or metallic, what additional test(s) should be carried out?

Firstly, I would perform a conductivity test. If the substance fails this test, it is covalent.

Secondly, this substance cannot be ionic because the boiling point of ionic solids are much higher than 140°C (e.g. LiCl's bp is around 1300°C).

Therefore, it has been concluded that this substance is a metallic solid.

[UnintentionalChaos]

First of all, do metals dissolve in water? That should make things a bit simpler.

Second, you have the right idea with a conductivity test, but how would you perform the test?

High melting point is often, but not always an indicator of ionic character. Take ionic liquids for example. Some of these ionic substances are "molten" at room temperature.

[Atome]

Thank you very much for your reply.

My revised answer:

I would place the solid substance in water. Since metals dissolve vigorously in water, the solid substance would be either an ionic or metallic solid if it passes this test. If it fails, it is a covalent solid.

(I am a little bit lost here on the conductivity of ionic and metallic solids) Next, I would check if the solution conducts electricity. If it conducts electricity, it would be a metallic solid since the electrons are traveling from the anode to the cathode?

[agrobert]

Metals don't dissolve in water, but they can react with water to form an ionic solution.  I doubt you would be given an unknown metal like sodium and if you were it would have to be stored in mineral oil or a hydrocarbon solvent.  Typical organics(covalently bound molecules) that dissolve in water are carboxylic acids and low chain alcohols.  Check the pH of your solution.

[Atome]

Thanks for your reply.

Unfortunately, the question does not provide the pH level of the substance. However, the question allows us to use any available lab equipment to determine if the solid substance is ionic, covalent, or metallic.

[Mitch]

Conductivity is a good one to see if its metallic, then dissolving it in water and seing if that solution is conductive would be good for ionic.