University:
University of Alberta
Course:
CHEM 101 | Introductory University Chemistry I
Academic year:

2024
Views:

71

Pages:

4
Author:

Neena N.

acids and bases Defining acids and bases The Brønsted-Lowry definition of acids and bases involves the transfer of hydrogen ions, H⁺. A Brønsted-Lowry acid is an H⁺ donor. A Brønsted-Lowry base is an H⁺ acceptor. For simplicity here, we will only refer to them as acids and bases. Here is an example reaction of an acid base reaction: HCl(aq) + NH3(aq) → NH4+ (aq) + Cl (aq) In this reaction: ● hydrochloric acid donates H⁺ to leave Cl and so the hydrochloric acid is an acid. ● the ammonia accepts the H⁺ ion to form + NH4, therefore ammonia is a base. Water as an acid or base Water demonstrates an interesting property - it can act as both an acid and a base. The equation below shows that water can both donate or accept hydrogens through an 'autoionisation' reaction. H2O + H2O → H3O+ + OHWater is said to be an amphiprotic molecule as it can either donate or accept a proton, thus acting either as an acid or a base. A common notation in acid-base reactions is using square brackets e.g. [OH]. These are shorthand for concentration. For example, [H3O+] means the concentration of H30+ ions Common acids and bases Here are some common acids and bases: Acids Bases hydrochloric acid sodium hydroxide nitric acid ammonia sulfuric acid pyridine acetic acid sodium carbonate phosphoric acid potassium hydroxide Lewis acid and base theory In the Lewis acid-base theory ● a Lewis acid is a species that acts as a lone pair acceptor ● a Lewis base is a species that acts as a lone pair donor Lewis acid A Lewis acid is a chemical species that has an electron-deficient atom and is capable of accepting an electron pair. It can do so by utilizing an empty orbital to form a coordinate covalent bond. Examples include metal cations, such as Al3+, Fe 3+ and H+, as well as molecules like BF3 and AICI3. These species are referred to as acids in the Lewis acid-base theory because they can accept a pair of electrons from a Lewis base. Lewis base A Lewis base is a chemical species that has a lone pair of electrons and is capable of donating that pair to form a coordinate covalent bond. Lewis bases are often molecules or ions with a lone pair on an electronegative atom. Examples include ammonia (NH3), water (H2O), and hydroxide ion (OH). They are referred to as bases in the Lewis acid-base theory because they can donate a pair of electrons to a Lewis acid. In Lewis acid-base reactions, a Lewis acid and a Lewis base come together, and the Lewis acid accepts the electron pair donated by the Lewis base to form a new coordinate covalent bond. This interaction allows for the formation of coordination complexes, acid-base reactions, and other chemical processes.