Passage VII

A carboxylic acid (CA) is a compound that contains a —COOH group. When a CA dissolves in H₂O, it can dissociate, as shown below.

An atom's electronegativity (EN) indicates the atom's ability to attract electrons within a molecule (see Table 1). The presence of an electronegative atom in a CA, and the atom's proximity to the —COOH group, can affect the acidity of a CA.

Table 2 gives the pH of aqueous 1.00 M (mole per liter) CA solutions at 25°C. The CA in each solution is either an acetic acid or a propanoic acid (see Figure 1), where X and Y each represent an atom listed in Table 1.

Tables adapted from James G. Speight, Lange's Handbook of Chemistry, 16th ed.©2005 by McGraw-Hill, Inc.