Question

What is an indicator? Describe what you would expect to see if one or two drops of phenolphthalein were added to solutions that were...
Neutral
Basic
Acidic

Answer 1

Any material that offers visual evidence of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution, generally by a colour change. A pointer or light on a device or instrument that shows pressure, volume, temperature, or the state of a piece of equipment (e.g., power on/off, available memory space) is another form of indication that may be found in chemistry and other disciplines.

Complete answer:
The chemical compound phenolphthalein has the formula ${{C}_{20}}{{H}_{14}}{{O}_{4}}$. In acid–base titrations, phenolphthalein is frequently employed as an indicator. It turns colourless in acidic solutions and pink in basic solutions for this purpose. It's a phthalein dye, which means it's a type of dye.
Phenolphthalein is water-insoluble and is generally dissolved in alcohols before being used in research. It's a weak acid with a tendency to lose ${{H}^{+}}$ ions in solution. Colorless is the nonionized phenolphthalein molecule, orange is the protonated phenolphthalein ion, and fuchsia is the deprotonated phenolphthalein ion. As ${{H}^{+}}$ ions are removed from a solution containing phenolphthalein and a base is added, the equilibrium between the nonionized and deprotonated states moves in favour of the deprotonated state.
Phenolphthalein is a pH indicator that changes colour depending on the pH of a solution. In a neutral or acidic solution, the indicator is clear and colourless. In a simple solution, it turns pink.
As a result, it will remain clear in a neutral solution.
It will remain transparent in an acidic solution.
It will turn pink in a basic solution.

Note:
A colourless reduced version of phenolphthalein, phenolphthalein, is used in the Kastle–Meyer test, which is used to detect compounds suspected of containing blood. A swab or filter paper is used to capture a dry sample. A few drops of alcohol are dropped onto the sample, followed by a few drops of phenolphthalein, and finally a few drops of hydrogen peroxide. Because phenolphthalein is produced when peroxide is added to a sample that includes haemoglobin, the sample will become pink very quickly. A positive test indicates that the sample contains haemoglobin, implying that it is most likely blood.