# An unknown solution changed the color of a phenolphthalein indicator from coloriess to pink. What would you comment about the pH of the unknown solution?

.....a solution whose $p H > 7$.
I found that phenolpthalein was one of the very best indicators to use for standard acid-base titrations, in that the acidic form is colourless, $\text{farblos}$, and the basic form is a lovely pink. The end-point is thus relatively simple to observe and detect. Of course, you titrate to the point of colour change, not to the colour change itself.