Question

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?

Answer 1

That you added a basic solution, i.e. .............

Explanation:

.....a solution whose `pH>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, `"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.