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A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. [1] Hence, a pH indicator is a chemical detector for hydronium ions (H 3 O +) or hydrogen ions (H +) in the ...
Paper form: It is a strip of coloured paper which changes colour to red if the solution is acidic and to blue, if the solution is basic. The strip can be placed directly onto a surface of a wet substance or a few drops of the solution can be dropped onto the universal indicator using dropping equipment.
However, for weak acids, a quadratic equation must be solved, and for weak bases, a cubic equation is required. In general, a set of non-linear simultaneous equations must be solved. Water itself is a weak acid and a weak base, so its dissociation must be taken into account at high pH and low solute concentration (see Amphoterism ).
Chemical reactions other than acid–base can also cause a color change to litmus paper. For instance, chlorine gas turns blue litmus paper white; the litmus dye is bleached [4] because hypochlorite ions are present. This reaction is irreversible, so the litmus is not acting as an indicator in this situation.
Amphoteric is derived from the Greek word amphoteroi (ἀμφότεροι) meaning "both".Related words in acid-base chemistry are amphichromatic and amphichroic, both describing substances such as acid-base indicators which give one colour on reaction with an acid and another colour on reaction with a base.
The difference in chemical structure that occurs in response to changes in pH, is the reason why anthocyanins often are used as pH indicators, as they change from red in acids to blue in bases through a process called halochromism.
A base was therefore a metal hydroxide such as NaOH or Ca(OH) 2. Such aqueous hydroxide solutions were also described by certain characteristic properties. They are slippery to the touch, can taste bitter [1] and change the color of pH indicators (e.g., turn red litmus paper blue).
In chemistry, an acid–base reaction is a chemical reaction that occurs between an acid and a base.It can be used to determine pH via titration.Several theoretical frameworks provide alternative conceptions of the reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory.