Question

Write down the changes that will be seen in the instance and explain the reason behind them. 

Two drops of the indicator phenolphthalein were added to a 10ml solution of sodium hydroxide.

Answer 1

Phenolphthalein is an indicator used for determining the quantity of base. When two drops of Phenolphthalein indicator are added to a 10 mL solution of Sodium hydroxide, the solution turns pink in colour because the acidic part of phenolphthalein reacts with the base, forming sodium salt of phenolphthalein which has a pink colour.

For example: In acid-base titration phenolphthalein is used to detect the endpoint of the base.