Video Transcript
Some acids can be classed as strong acids. Which of the following is not an example of a strong acid? (A) Hydroiodic acid, HI. (B) Hydrobromic acid, HBr. (C) Hydrochloric acid, HCl. (D) Nitric acid, HNO3. Or (E) benzoic acid, C6H5COOH.
It can be difficult to tell if an acid is strong or weak just by looking at it. However, one thing we can look for is if the acid is organic or inorganic. Acids that are organic contain carbon-to-hydrogen bonds. Organic acids tend to be weak acids. Inorganic acids do not contain carbon-to-hydrogen bonds. In fact, most inorganic acids do not contain carbon at all. Acids that are considered strong tend to be inorganic.
Let’s apply this information by looking at the chemical formulas of all of our answer choices. Hydroiodic, hydrobromic, hydrochloric, and nitric acid are all inorganic acids. These acids completely dissociate in water. Therefore, they are considered to be strong acids by the Arrhenius definition. In solution, strong acids will have a high amount of dissociated products, whereas weak acids do not.
Benzoic acid is the only organic acid from the answer choices. Benzoic acid is a weak acid and would only partially dissociate in water. We can represent this using the equilibrium arrow. Therefore, of the acids given, the acid that is not an example of a strong acid is answer choice (E), benzoic acid, C6H5COOH.
