An acid can be completely neutralized by a base when the pH of the resultant solution becomes neutral, which is 7 on the pH scale. When the acid is completely neutralized, the solution is said to have reached its endpoint. Some common indicators can also be used to precisely determine the endpoint of an acid-base titration, such as litmus, phenolphthalein, or methyl orange, by observing the change in color when neutralization is achieved.