Question

Which compound is a weak acid?
a.HNO₃
b.HBr
c.HC₆H₅O₂
d.H₂SO₄

Answer 1

HC₆H₅O₂, or benzoic acid, is the weak acid among the options given, as it does not ionize completely and exists in equilibrium with its ionized form in solution.

Step-by-step explanation:

The student asked which compound is a weak acid among the given options: HNO₃, HBr, HC₆H₅O₂, and H₂SO₄. HNO₃ (nitric acid) and H₂SO₄ (sulfuric acid) are strong acids, which ionize completely in water. HBr, or hydrobromic acid, is also a strong acid. In this case, HC₆H₅O₂ (also known as benzoic acid) is the correct answer since it is a weak acid that does not ionize completely in water and exists at equilibrium with its ionized form.

Answer 2

HC₆H₅O₂ (benzoic acid) is the weak acid among the listed compounds. Strong acids like H₂SO₄ and HNO₃ ionize completely, while weak acids like HC₆H₅O₂ do not.

So, the correct answer is C.

Step-by-step explanation:

Out of the given options, HC₆H₅O₂ is the compound that is a weak acid. This compound is also known as benzoic acid. Other compounds listed, such as H₂SO₄ (sulfuric acid) and HNO₃ (nitric acid), are classified as strong acids because they disassociate completely in aqueous solutions, releasing a large amount of H⁺ ions.

In contrast, weak acids only partially ionize in solution, which means they do not release all their available hydrogen ions into the solution. The weak ionization of benzoic acid is represented by the equilibrium equation:

HC₆H₅O₂(aq) + H₂O(l) ⇔ H₃O+ (aq) + C₆H₅O₂⁻ (aq).

HB nknown is considered incorrect because it is not a conventional representation of an acid.

So, the correct answer is C.