Biology 101 Lab Introduction to Acids, Bases, and pH As an online student, read the directions, answer questions 1 - 3, complete the color table and...

But...add an acid

>      OH-

       H+

Or add a base

                                                           H+       <

                                                                               OH-

Important facts about the pH scale:

·        The pH scale ranges from 0 to 14

·        The pH scale is logarithmic. That is, a change of 1 pH unit represents a 10-fold change in hydrogen ion concentration. 

·         The pH scale is "inverted"—a lower pH means a higher concentration of H+

                                             a higher pH means a lower concentration of H+

·        Solutions with pH = 7 are neutral (for example, pure water)

·        Solutions with pH < 7 are acidic

·        Solutions with pH > 7 are basic (or "alkaline")

An acid is a substance that releases or causes the release of H+ into solution.

Solutions that have pH values lower than 7 are considered to be acids. Some common acids are hydrochloric acid, acetic acid, carbonic acid, and sulfuric acid. All of these compounds contain hydrogen. When the compound is dissolved in water, hydrogen ions are released, and the pH of the solution is low. View the image of phenol red tubes to observe the tubes and answer the following questions.

1. What color is the phenol red solution initially? (This solution is shown in the middle of the image of phenol red tubes.)