What color is phenolphthalein in a basic solution?
pH is a measure of the H3O + concentration. A neutral solution: Has a pH of exactly 7. Contains equal amounts of hydronium ions and hydroxide ions. Pure Water: 2H2O H3O + + OH – An acid solution: Has a pH lower than 7. Contains more hydronium ions than hydroxide ions. The farther from 7, the stronger the acid. A basic solution: Has a ph higher than 7. Contains more hydroxide ions than hydronium ions. The farther from 7, the stronger the base. Indicators: Compounds that show a color change in an acid or base. Most indicators are weak organic acids or bases that react with ions in solution. It is this chemical reaction that produces the color change. Indicators are used to determine the approximate pH of a substance. Two common indicators are: • Litmus – • Acids turn blue litmus red. • Bases turn red litmus blue. • Phenolphthalein – • Colorless in an acid. • Very faint pink in a neutral solution. • Bright pink in a base. pH Meter: A device used to measure the exact pH of a solution. Test
