Question

1 Acidity is a measure of the amount of dissolved _____ ions in a solution.

• hydrogen

• hydroxide

• sodium

• calcium

2. Why is phenolphthalein added to an unknown acid before conducting a titration experiment?

• To speed the reaction of chemicals

• To serve as a pH indicator

• To neutralize the acid

Answer 1

1. Acidity is a measure of the amount of dissolved hydrogen ions in a solution.

If the amount of hydrogen ions in the solution is high the solution is acidic. While the basicity is a measure of the amount of dissolved hydroxide ions in a solution.

2. Phenolphthalein is added to an unknown acid before conducting a titration experiment To serve as a pH indicator.

​​​​​​To determine the concentration of an unknown acid, titration is done of it with a known base solution. Phenolphthalein is added to the solution to indicate the end point( colourless solution). when all the acid present in the unknown solution is react with the base than on adding a drop of a base makes the solution basic. In basic condition phenolphthalein color is pink which indicates the end point.