The given experiment in which phenolphthalein indicator was added to a sample solution that turned pink and then added several 20.00 mL aliquots of 0.100 M HCl to the sample solution until the pink color disappeared and finally added dropwise a 0.094 4 M solution of NaOH from a buret into the colorless sample solution until the faintest pink color reappeared is an example of an acid-base titration.What is an Acid-Base titration?Acid-Base titration is a technique used to determine the unknown concentration of an acid or base by neutralizing it with a solution of a known concentration. A titration involves adding a measured volume of a solution with a known concentration to a solution with an unknown concentration until the reaction is complete. The point at which the reaction is complete is called the endpoint, which is determined by a change in color in an indicator such as phenolphthalein.