CHEMEStRY QUESTION!!?

Question

What effect does carbon dioxide have on a half full test tube of phenolphthalein and WHY?

Answer 1

CO2 will react with water(H2)) to form carbonic acid(H2CO3) which will acidify the solution. Phenolphthalein is an acid-base indicator that is clear in acidic solution and turns pink when the solution turns basic. Since you don't state whether the starting solution is acidic or basic, there is no way to answer your question other than to say either no change or it will turn clear.

Answer 2

carbon dioxide tends to make solutions more acidic because of the way it dissolves in water.

H2O+CO2-->H2CO3

H2CO3 is a weak acid and thus will partly dissociate into H+ and HCO3-. This will cause the solution to be more acidic. Now if I remember correctly, the phenolphthalein will become clear as the solution gets acidic.