Acids and Bases
Acids and Bases
Many acidic and basic solutions are colorless and odorless. There are molecular substances called indicators that change color when they come into contact with acids or bases.
Acids:
Bases:
Substances with a pH 0-7 are acids, while substances with a pH 7-14 are called bases. Substances in the middle (7) are neutral.
The pH scale
The pH scale is a logarithmic scale that describes the concentration of H⁺ ions in a solution. pH is related to [H⁺] by the formula:
pH = -log[H⁺]
In any solution, the product of the hydrogen ion, H⁺, concentration and hydroxide ion, OH⁻, concentration is a constant.
-Water dissociates into H⁺ and OH⁻ ions.
The pH scale is a logarithmic scale that describes the concentration of hydrogen ions, H⁺ , in solution: pH = -log[H⁺]. The H⁺ concentration is related to the OH⁻ concentration:
[H⁺][OH⁻] =10⁻¹⁴. As [H⁺] increases, [OH⁻] decreases, and vice-versa. The pH of water is 7. In water the H⁺ concentration is equal to the OH⁻ concentration. Thus, water is neutral.