One of the most important quantities in connection with acids and bases is the pH value . It is a measure of the concentration of hydrogen ions (or hydronium ions) in a solution - pay someone to do my math homework . If the pH value is < 7, the solution reacts acidically; if, on the other hand, it is in the range > 7, one speaks of an alkaline or basic solution. Neutral solutions are solutions whose pH value is 7.
To determine the pH value of a solution, one can work with special measuring instruments (pH meter, potentiometer). Another possibility is to add a water-soluble dye to the solution, the colour of which changes depending on the pH of the solution.
Acid-base indicators and their mode of action
Such dyes are called indicators (Latin: indicare = to indicate). The most common ones in chemistry are acid-base indicators, which are used not only to indicate the pH value but also to determine the so-called equivalence point of acid-base titrations - do my homework . The procedure of such titrations for the quantitative determination of the acid or base content of a solution is explained in another article on this CD.
The indicators used in acid-base titrations are themselves weak organic acids or bases - statistics homework help , but they change colour at different hydronium ion concentrations c(H3O+). The colour change is based on the fact that structural changes of the compounds occur due to the proton exchange, which lead to a colour change of the substance.
In the following general example equation, "IndH" stands for the indicator in the formula. The H makes it clear that it is an acid.