A pH indicator is a halochromic chemical compound that is added in small amounts to a solution to determine the pH of the solution visually or spectroscopically by changes in absorption and/or emission properties. It is a chemical detector for hydronium ions (H3O+) or hydrogen ions (H+) in the Arrhenius model. The pH value of a neutral solution is 7.0 at 25°C (standard laboratory conditions) . Solutions with a pH value below 7.0 are considered acidic, and solutions with a pH value above 7.0 are basic.
A pH indicator is usually a weak acid that exists as a natural dye and indicates the concentration of H+ (H3O+) ions in a solution via color change/Acids_and_Bases/Acid_and_Base_Indicators/PH_Indicators). A pH value is determined from the negative logarithm of this concentration and is used to indicate the acidic, basic, or neutral character of the substance being tested/Acids_and_Bases/Acid_and_Base_Indicators/PH_Indicators). pH indicators exist as liquid dyes and dye-infused paper strips/Acids_and_Bases/Acid_and_Base_Indicators/PH_Indicators). They are added to various solutions to determine the pH values of those solutions. Whereas the liquid form of pH indicators is usually added directly to solutions, the paper form is dipped into solutions and then removed for comparison against a color/pH key.
pH indicators are specific to the range of pH values one wishes to observe/Acids_and_Bases/Acid_and_Base_Indicators/PH_Indicators). Common indicators such as phenolphthalein, methyl red, and bromothymol blue are used to indicate pH ranges of about 8 to 10, 4.5 to 6, and 6 to 7.5, respectively/Acids_and_Bases/Acid_and_Base_Indicators/PH_Indicators). Phenolphthalein ranges from colorless to pink, methyl red ranges from red to yellow, and bromothymol blue ranges from yellow to blue/Acids_and_Bases/Acid_and_Base_Indicators/PH_Indicators). A universal indicator is a pH indicator made of a solution of several compounds that exhibit various smooth color changes over a wide range of pH values to indicate the acidity or alkalinity of solutions. The colors from yellow to red indicate an acidic solution, colors blue to violet indicate an alkaline solution, and a green color indicates that a solution is neutral.
In summary, a pH indicator is a chemical compound that changes color in solution over a narrow range of pH values, indicating the acidity or basicity of the solution. It is used to estimate the pH of a chemical solution and can be found in liquid dyes and dye-infused paper strips. pH indicators are specific to the pH range that is desired to be observed, and they are frequently employed i...
