Science, Tech, Math › Science Acidic Solution Definition Acidic Solutions in Chemistry Share Flipboard Email Print Blue litmus paper turns red under acidic conditions, while red litmus paper turns blue under basic conditions. David Gould, Getty Images Science Chemistry Basics Chemical Laws Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter 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.