Acidic Solution Definition

Acidic Solutions in Chemistry

Blue litmus paper turns red under acidic conditions, while red litmus paper turns blue under basic conditions.
Blue litmus paper turns red under acidic conditions, while red litmus paper turns blue under basic conditions. David Gould, Getty Images
by Anne Marie Helmenstine, Ph.D.
Updated February 12, 2018

In chemistry, any aqueous solution can be classified as belonging to one of three groups: acidic, basic, or neutral solutions.

Acidic Solution Definition

An acidic solution is any aqueous solution which has a pH < 7.0 ([H+] > 1.0 x 10-7 M). While it's never a good idea to taste an unknown solution, acidic solutions are sour, in contrast to alkaline solutions, which are soapy.

Examples: Lemon juice, vinegar, 0.1 M HCl, or any concentration of an acid in water are examples of acidic solutions.