Student Exploration: Titration

Vocabulary: By the end of the Gizmo, please familiarize yourself with the following analyte titrant equivalence point indicator Prior Knowledge Questions (Do these BEFORE using the Gizmo.) There are several definitions of acids and bases. According to the Brønsted-Lowry definition, an acid is a substance that is capable of donating a proton to another substance. A base is a substance that accepts protons. When an acid and a base are combined, the acid is neutralized as the base accepts the protons produced by the acid. One way to determine if a solution is acidic or basic is to use litmus paper, as shown above. There are two types of litmus papers: red and blue. How does litmus paper indicate an acid? Blue litmus paper turns red How does litmus paper indicate a neutral substance? No Change How does litmus paper indicate a base? Red litmus paper turns blue Gizmo Warm-up Litmus is an example of an indicator, a substance that changes color depending on its pH (pH is a measure of the concentration of protons, or H+ ions). In the Titration Gizmo™, you will use indicators to show how acids are neutralized by bases, and vice versa. To begin, check that 1.00 M NaOH is selected for the Burette(titrant), Mystery HBr(analyte) is selected for the Flask, and Bromthymol blue is selected for the Indicator. 1. Look at the flask. What is the color of the bromthymol blue indicator? Yellow 2. What does this tell you about the pH of the solution in the flask? Its Acidic Solutions with a pH below 7.0 are acidic, while those with a pH above 7.0 are basic. 3. Move the slider on the burette to the top to add about 25 mL of NaOH to the flask. What happens, and what does this tell you about the pH of the flask? It turned blue