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Multiple Choice
Which of the following is the strongest acid in aqueous solution?
A
Ammonia (NH3)
B
Hydrochloric acid (HCl)
C
Acetic acid (CH3COOH)
D
Water (H2O)
Verified step by step guidance
1
Identify the nature of each compound: Ammonia (NH3) is a weak base, Hydrochloric acid (HCl) is a strong acid, Acetic acid (CH3COOH) is a weak acid, and Water (H2O) is neutral.
Understand the concept of acid strength: In aqueous solutions, a strong acid completely dissociates into its ions, while a weak acid only partially dissociates.
Compare the dissociation of each compound in water: HCl dissociates completely into H⁺ and Cl⁻ ions, making it a strong acid. CH3COOH partially dissociates into CH3COO⁻ and H⁺ ions, making it a weak acid. NH3 does not dissociate to produce H⁺ ions, and H2O is neutral.
Consider the pKa values: Strong acids have lower pKa values. HCl has a very low pKa, indicating strong acidity, while CH3COOH has a higher pKa, indicating weaker acidity.
Conclude based on dissociation and pKa: Since HCl dissociates completely and has the lowest pKa, it is the strongest acid among the given options in aqueous solution.