Video Transcript
Which of the following solutions is considered a nonelectrolyte? (A) Acetic acid, (B) ammonium hydroxide, (C) ethyl alcohol, or (D) potassium hydroxide.
All of the given substances are solutions. A solution is a homogeneous mixture with a uniform composition throughout. A solution is composed of at least one solute and a solvent. A solute is the minor component of a solution that is being dissolved in the solvent, which is the major component of a solution. And we can think of it as the substance that is doing the dissolving. Water is one of the most common solvents used and is even sometimes referred to as the universal solvent, since it can dissolve so many different substances.
This question is asking us to identify the substance that is considered a nonelectrolyte. A nonelectrolyte is a substance that does not have freely moving ions that can conduct electricity when molten or dissolved in water. So oppositely, if a substance is an electrolyte, it does have freely moving ions that can conduct electricity when molten or dissolved in water. Since nonelectrolytes and electrolytes involve the absence or presence of ions in water, we know that the substances given must be solutions with the solvent being water. Let’s have a look at how each substance would behave in water to determine which is the nonelectrolyte.
Answer choice (A) acetic acid can be represented using its condensed formula CH3COOH. In water, acetic acid partially dissociates into ions. We can represent this behavior using the equilibrium arrow. This means that some of the acetic acid molecules ionize in water, but many do not. Because this solution does have freely moving ions in water, it is classified as an electrolyte. But because of the partial dissociation, it is considered a weak electrolyte. But because it still contains freely moving ions in solution, it would still conduct electricity to some degree. We can eliminate answer choice (A).
Answer choice (B) ammonium hydroxide can be represented by its chemical formula NH4OH. In water, ammonium hydroxide partially dissociates into ammonium and hydroxide ions. As we saw with acetic acid, ammonium hydroxide is a weak electrolyte as it would conduct electricity to some degree due to the freely moving ions. We can eliminate answer choice (B).
Answer choice (C) ethyl alcohol can be represented using its condensed formula CH3CH2OH and is an organic covalently bonded compound that exists as a liquid at room temperature. Ethyl alcohol when added to water can dissolve and mix. However, it does not form freely moving ions and therefore would not conduct electricity. Ethyl alcohol is a nonelectrolyte. Answer choice (C) is the correct answer, but let’s rule out answer choice (D) just to be sure.
(D) Potassium hydroxide can be represented using its chemical formula KOH and in water ionizes completely into potassium and hydroxide ions. Because a solution of potassium hydroxide would have many freely moving ions, it would conduct electricity strongly and be classified as a strong electrolyte. We can eliminate answer choice (D).
Therefore, the solution that will be considered a nonelectrolyte would be answer choice (C) ethyl alcohol.
