Final answer:
Acids and bases have been defined by Svante Arrhenius as substances that produce hydrogen ions and hydroxide ions, respectively, in solution. Later, Johannes Brønsted and Thomas Lowry expanded this definition, creating the Brønsted-Lowry theory, which identifies acids as proton donors and bases as proton acceptors. This broader definition encompasses all Arrhenius acids and bases and includes additional substances like ammonia.
Step-by-step explanation:
Definitions of Acids and Bases
The understanding of acids and bases has evolved over time with contributions from various chemists. Svante Arrhenius proposed that acids are substances that produce hydrogen ions (H+) when dissolved in water, while bases produce hydroxide ions (OH-). However, this definition was limited because it did not account for acid-base behavior in the absence of water. Seeking a more inclusive definition, Johannes Brønsted and Thomas Lowry introduced a broader concept in 1923. According to the Brønsted-Lowry theory, acids are proton donors and bases are proton acceptors. This theory expanded the list of substances classified as acids or bases to include those that do not produce hydroxide ions, such as ammonia (NH3). While all Arrhenius acids and bases are also Brønsted-Lowry acids and bases, the converse is not true. Some Brønsted-Lowry acids and bases do not fit the strict Arrhenius definition because they do not result in H+ or OH- in water. To identify the Brønsted-Lowry acid, its conjugate base, the Brønsted-Lowry base, and its conjugate acid in a reaction, one must look at the transfer of protons between the reactants.