The most suitable indicator for the reaction between NaOH and HCOOH is?

The best indicator for the reaction between NaOH (sodium hydroxide) and HCOOH (formic acid) is phenolphthalein. Phenolphthalein is a pH indicator that changes color based on the acidity of the solution. In an acidic solution, it is colorless, while in a basic (alkaline) solution, it turns pink or red. This makes it ideal for monitoring the progress of a reaction between an acid and a base. As the reaction between NaOH and HCOOH proceeds and the concentration of hydroxide ions increases, the solution will become more basic, causing the phenolphthalein to change color, indicating that the reaction is complete.