One such indicator, phenolphthalein (C20H14O4), is clear and colorless in acidic solutions but turns deep pink in basic solutions if the pH is higher than 8.2 (Figure 10-9). The fact that phenolphthalein changes color a little above 7.0 usually leads to only very small error in the experiment.
Keeping this in consideration, what is the color of phenolphthalein in a neutral solution?
Phenolphthalein changes colour sharply at about pH 8. For most purposes, this means that it is pink in alkaline solutions and colourless in acidic solutions. Note that it would be incorrect to say that it is 'clear' in acidic solutions.
What color is phenolphthalein at pH 7?
Phenolphthalein changes color at pH ~9. Bromothymol blue has a pKn value of 7.1. At pH 7, its color changes from yellow to blue.
Is phenolphthalein an acid?
Phenolphthalein is an indicator of acids (colorless) and bases (pink). Sodium hydroxide is a base, and it was in the pitcher at the beginning, so when added to the phenolphthalein in beakers 2 and 4, it turned pink (top half of the graphic). The equilibrium shifts right, HIn decreases, and In- increases.