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, Mystery HBr is selected for the Flask, and Bromthymol blue is selected for the Indicator.
Calculate: Concentration is measured by molarity (M), or moles per liter. Brackets are also used to symbolize molarity. For example, if 0.6 moles of HNO3 are dissolved in a liter of water, you would say [HNO3] = 0.6 M.
Because HNO3 is a strong acid, it dissociates almost completely in water. That means the concentration of H+ is very nearly equal to that of HNO3.What is [H+] if [HNO3] is 0.01 M? 0.01 M
The pH of a solution is equal to the negative log of H+ concentration: pH = –log[H+]
Describe: The equation for the reaction of nitric acid (HNO3) and sodium hydroxide (NaOH) is shown on the bottom right of the Gizmo.
Measure: A titration can be used to determine the concentration of an acid or base by measuring the amount of a solution with a known concentration, called the titrant, which reacts completely with a solution of unknown concentration, called the analyte. The point at which this occurs is called the equivalence point.
Explain: A titration curve is a graph of pH vs. volume of titrant. The graph at right shows a typical titration curve for the titration of a strong acid by a strong base. (A strong base is one that has relatively high dissociation in water.)
According to theBrønsted-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? Both strips turn red.
