What is the primary factor determining the character of an acid?

The character of an acid is primarily determined by its ability to donate protons (H⁺ ions) in a solution, which is fundamentally linked to its electron affinity. Electron affinity reflects how readily an atom or molecule can accept electrons, which influences the stability of the corresponding anions formed when an acid donates a proton. A strong acid is characterized by a high tendency to lose a proton and form a stable conjugate base, which is associated with a greater electron affinity.

When an acid donates a proton, it leaves behind a negatively charged conjugate base; the stability of this base largely depends on its ability to accommodate the additional negative charge. A higher electron affinity for the element or molecule will contribute to the stability of that conjugate base, thus making the original acid stronger.

In contrast, factors such as the solvent's temperature can influence reaction dynamics but do not fundamentally define acid strength, and the molecular size of the acid might affect steric factors or solubility but are not direct indicators of acid character. Proton gain enthalpy, while related to acid-base behavior, does not specifically address the tendency to lose protons, which is essential for determining acid character. Therefore, the influence of electron affinity provides a clearer and more direct