Advanced Placement (AP) Chemistry Practice Exam

The strength of an oxoacid generally increases with?

1. The number of hydrogen atoms.

2. The number of oxygen atoms.

3. The concentration of the acid.

4. The temperature of the solution.

The correct answer is: The number of oxygen atoms.

The strength of an oxoacid typically increases with the number of oxygen atoms attached to the central atom in the acid. This is primarily because additional oxygen atoms increase the overall electronegativity of the central atom and contribute to the stability of the conjugate base formed when the acid donates a proton (H+). In an oxoacid, as more oxygen atoms are present, they allow for greater delocalization of the negative charge that results from deprotonation. This delocalization stabilizes the conjugate base, making it more favorable for the oxoacid to donate a proton, which increases the acid's strength. The other options, while they relate to aspects of acid strength, do not systematically govern the strength of oxoacids in the same way. The number of hydrogen atoms does not directly affect the acidic strength; instead, it's the ability to lose those protons that matters. Concentration can affect the observed strength of an acid in a particular solution but does not alter the intrinsic strength of the acid itself. Temperature can influence reaction rates and equilibria but also does not inherently change the acid's identity or its strength in the context of oxoacids. Therefore, the increase in the number of oxygen