Advanced Placement (AP) Chemistry Practice Exam

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Study for the AP Chemistry Exam with targeted quizzes and interactive questions. Gain expertise with detailed explanations for each question and boost your confidence before the test day!

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Which term describes a substance that can donate a proton?

Arrhenius base
Brønsted-Lowry acid
Lewis acid
Arrhenius acid

The correct answer is: Brønsted-Lowry acid

The term that best describes a substance capable of donating a proton is a Brønsted-Lowry acid. This definition is rooted in the Brønsted-Lowry theory of acids and bases, which defines acids as proton donors and bases as proton acceptors. When an acid donates a proton (H+), it transforms into its conjugate base, illustrating the fundamental aspect of this theory. This concept is foundational in acid-base chemistry as it broadens the understanding beyond the specific reactions outlined by the Arrhenius definition, which only considers acids as substances that produce H+ in water. Furthermore, the definitions of Lewis acids and bases focus on electron pair donation and acceptance, which does not specifically address proton transfer. Thus, the Brønsted-Lowry theory most accurately characterizes the behavior of substances donating protons.