Why and when phenolphthalein used as the indicator?

Answer 1

There are a lot of indicators around. Choosing which one to use depends on what you're analyzing for, what pH the endpoint happens at, what kind of reaction is happening in the flask, etc.

Some common ones are Methyl Orange, Methyl Red, Starch, Bromphenol Blue; the list goes on.

Answer 2

Usually in titrations involving amines as the titrator or titrant. Phenolpthalein changes colour at around pH 9 which is commonly the pH at which an amine neutralises. You usually use it when you titrate an acid with an amine - that is adding an amine to an acid because the colour change from clear to pink/purple is easier to determine.

Answer 3

It changes color in the presence of acids and bases. So it can be used to determine whether a substance is acidic or basic. It can be used in titrations to determine the actual concentration of the substance being investigated. According to Wikipedia, when the pH is less than zero, phenolphthalein it will turn orange; when the pH is 0-8.2, it is colorless; and when the pH is 8.2-12.0 it is pink to fuschia; and when the pH is greater than 12.0 is is colorless.

Answer 4

Phenolphthalein is commonly used as an indicator in acid-base titrations because it changes color at a pH range of about 8.2-10.0, making it ideal for detecting the endpoint of the titration. It is often used in titrations for weak acids and strong bases, such as in the titration of a strong base with a weak acid.

Answer 5

A solution of phenolphthalein remains colourless in acids or neutral liquids, but turns bright reddish/pink in alkalis.

Answer 6

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