CLASS 9 · LEARNING KNOWLEDGE
pH value and indicators – basic principles
How it works
The pH value indicates how acidic or basic a solution is. It typically ranges from 0 (strongly acidic) to 14 (strongly basic), with 7 considered neutral. Acids have a pH value below 7, bases above 7. Indicators are dyes that change color depending on the pH value and thus show whether a solution is acidic, neutral, or basic. Well-known indicators are litmus, phenolphthalein, and universal indicator. The concentration of hydrogen ions (H+) determines the pH value.
Note
The pH value of an aqueous solution indicates how acidic or basic it is: pH < 7 = acidic, pH = 7 = neutral, pH > 7 = basic. Indicators show the approximate pH range through a change in color.
The pH value of an aqueous solution indicates how acidic or basic it is: pH < 7 = acidic, pH = 7 = neutral, pH > 7 = basic. Indicators show the approximate pH range through a change in color.
An example
What color does universal indicator typically show in a neutral solution (pH 7)?
Universal indicator usually shows a green color at pH 7, as this marks the neutral range.
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50 Exercises
To the learning unit →Own explanation and own practice exercises by AmyMath. Subject reference framework: Chemistry. The topic assignment may vary by federal state.