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Multiple Choice
Which of the following compounds is the strongest acid?
A
Acetic acid (CH3COOH)
B
Phenol (C6H5OH)
C
Hydrochloric acid (HCl)
D
Water (H2O)
Verified step by step guidance
1
Identify the functional groups present in each compound: Acetic acid contains a carboxylic acid group, phenol contains a hydroxyl group attached to an aromatic ring, hydrochloric acid is a simple binary acid, and water is a neutral molecule with two hydrogen atoms bonded to oxygen.
Understand the concept of acidity: Acidity is determined by the ability of a compound to donate a proton (H⁺). The stronger the acid, the more readily it donates a proton.
Consider the stability of the conjugate base: A strong acid has a stable conjugate base. For example, the chloride ion (Cl⁻) from hydrochloric acid is very stable, making HCl a strong acid.
Compare the acidity of the compounds: Hydrochloric acid (HCl) is a strong acid because it completely dissociates in water, releasing H⁺ ions. Acetic acid and phenol are weak acids as they do not fully dissociate. Water is neutral and not considered an acid in this context.
Conclude based on the dissociation and stability: Since hydrochloric acid dissociates completely and has a stable conjugate base, it is the strongest acid among the given options.