Kaplan Nursing Entrance Practice Exam

According to Arrhenius theory, what is an acid?

1. A species that accepts protons

2. A species that produces OH-

3. A species that produces H+ in aqueous solutions

4. A compound that donates electrons

The correct answer is: A species that produces H+ in aqueous solutions

According to Arrhenius theory, an acid is defined as a species that produces H⁺ ions when dissolved in aqueous solutions. This definition highlights the behavior of acids in water, where they increase the concentration of hydrogen ions. The presence of these H⁺ ions is what characterizes acidic solutions, leading to properties such as a tangy flavor, the ability to conduct electricity, and a propensity to react with bases to form water and salts. In this context, the understanding of acids is foundational to grasping broader concepts in acid-base chemistry, as it sets the groundwork for interactions with other chemical species, including bases, which are defined as substances that produce OH⁻ ions in water. The Arrhenius theory thus provides a straightforward classification that remains useful in many practical applications, such as in titrations and pH measurement.