1. Acid Base Titrations

2. What is it? • Titration is an experiment where a known property of one solution is used to infer an unknown property of another solution. • Calculate the amount of unknown acid in the receiving flask by measuring the amount of base, or titrant, it takes to neutralize the acid. • There are two major ways to know when the solution has been neutralized. • The first uses a pH meter in the receiving flask adding base slowly until pH reaches equivalence point • The second method uses an indicator

3. Titration Vocabulary • Titrant • The substance added to the analyte in a titration (reagent solution) • Analyte • The substance being analyzed • Equivalence point • The point in a titration at which the quantity of titrant is exactly sufficient for stoichiometric reaction with the analyte.

4. Titration Vocabulary cont’d • End point • The point in a titration at which there is a sudden change in a physical property, such as indicator color, pH, conductivity, or absorbance. Used as a measure of the equivalence point. • Indicator • A compound having a physical property (usually color) that changes abruptly near the equivalence point of a chemical reaction.

5. Choosing Indicators For Titrations will depend on the overall pH of the salt produced

6. TITRATION CURVES • A titration curve is drawn by plotting data attained during a titration, titrant volume on the x-axis and pH on the y-axis. The titration curve serves to profile the unknown solution. • http://www.succeedingwithscience.com/labmouse/chemistry_a2/2308.php

7. STRONG ACID VS STRONG BASE • equivalence point is exactly 7 because the salt produced does not undergo any hydrolysis reactions. • Which indicator • can be used?

8. Strong Acid & Strong Base 4 3 2 1

9. Strong Acids and Strong Base Titrations Example: HCl (strong acid) and NaOH (strong base) Formula Equation:__________________________________ Complete Ionic Equation: ____________________________ Net Ionic Equation:__________________________________ pH at equivalence point: _____________________________ Possible Indicators:__________________________________

10. Strong Base vs weak acid Because the Salt is basic, the pH will be greater than 7 at the equivalence point. pH range = 8-9

11. Weak Acid & Strong Base E.P > 7 pH starts higher as CH3COOH is a weaker acid

12. Finding Ka from the graph • The half-equivalence point is when just enough base is added for half of the acid to be converted to the conjugate base. When this happens, the concentration of H+ ions equals the Kavalue of the acid. Take this one step further, pH = pKa.

13. Strong acid vs weak base EP is less than 7, it is about 5.5 Which indicator is used?

14. Choosing an Indicator: