Which of the following substances best conducts electricity? A) Na₂CO₃ solid, B) C₆H₁₂O₆ aqueous, C) C₂H₅OH aqueous, D) KI solid, or E) LiCl liquid.
Na₂CO₃ is the symbol for sodium carbonate. C₆H₁₂O₆ is the chemical formula for glucose, although there are other chemicals with this chemical formula. However, they’re all very similar. So I’ll just use glucose in this case. C₂H₅OH is the chemical symbol for ethanol, which is commonly simply called alcohol. Meanwhile, KI is the chemical symbol for potassium iodide, while LiCl is the chemical formula for lithium chloride.
Now that we’ve looked over the names, let’s have a look at what we’re going to apply them to, conducting electricity. Electricity is simply the flow of charge, usually electrons, due to a difference in their potential. For instance, if we have an electrical circuit with a battery and a bulb, the battery generates high-energy electrons on one side. These high-energy electrons push energy through the circuit. A little gets lost in the wiring. And a lot is lost as components convert the electrical energy into other forms of energy, like light. A substance in this setting is said to conduct electricity if it allows the electrons to flow. If the substance doesn’t allow electrons through, it’s said to be an insulator.
Now let’s have a look at each of our substances and see what happens when they’re exposed to a potential difference. Sodium carbonate in its solid form is an ionic lattice. The ionic lattice is made up of sodium ions and carbonate ions. However, these ions aren’t free to move because we’re dealing with a solid. This means that charge cannot flow. So even if we bridge the electrical contacts with sodium carbonate, nothing would happen.
The question asks for the substance that best conducts electricity. But we’re unlikely to find anything that’s substantially worse than sodium carbonate. So sodium carbonate cannot be the right answer.
C₆H₁₂O₆ contains only nonmetal elements. Therefore, we’d expect it to be a covalent compound. This substance would be dissolved in water. But pure water is nonconductive. We need to add something like sodium chloride, a salt, to water to make it conductive. Organic compounds require specific functional groups like carboxylic acid in order to ionize in water and make the water conductive. But simple sugars like glucose do not have these functional groups. So our solution of C₆H₁₂O₆ would also be nonconductive and therefore is not a correct answer.
The formula C₂H₅OH is the chemical formula for ethanol, which, like glucose, does not contain functional groups which ionize in water. So a solution of ethanol would also not conduct electricity.
Potassium iodide in its solid form is another example of an ionic lattice. So like sodium carbonate, it would not allow charge to flow.
This just leaves lithium chloride in its liquid state, which would contain mobile lithium ions and chloride ions. If we put a potential difference across two electrodes in a molten lithium chloride bath, the ions would migrate to the corresponding electrode. Lithium plus to the negative electrode and Cl minus to the positive. This would allow for a flow of charge through the medium, meaning lithium chloride in its liquid form is conductive. Although in order to have a sustained flow of charge, we would need a chemical reaction to be going on at the electrodes. We’d likely convert lithium ions into lithium metal and chloride ions into chlorine gas.
Our top candidate for the substance that best conducts electricity out of this set is lithium chloride in its liquid form.