15.2 DETERMINING pH AND TITRATIONS

15.2 What are 2 ways of determining the pH of a solution?

15.2 The pH of a solution can be determined by: Indicators are a combination of a weak acid and a weak base that change colors at a certain pH (transition interval). Each indicator is unique in the colors that it shows. p. 513

15.2 The pH of a solution can be determined by: Indicators are a combination of a weak acid and a weak base that change colors at a certain pH (transition interval). Each indicator is unique in the colors that it shows. Universal indicator is a mixture of several different indicators, so it has a wide variety of colors. pH meters are electrodes that measure the conductivity of a solution by using the [H3O1+].

15.2 What is a titration?

15.2 A titration is a controlled neutralization reaction. Indicators or a pH meter are used to identify when neutralization occurs. What is the equivalence point?

15.2 A titration is a controlled neutralization reaction. Indicators or a pH meter are used to identify when neutralization occurs. The equivalence point occurs when the number of H3O1+ equals the number of OH1-. If an indicator is used in a titration, it must change color approximately at the pH of the equivalence point. (The end point is the volume where the indicator changes colors.)

15.2 A titration is a controlled neutralization reaction. Indicators or a pH meter are used to identify when neutralization occurs. The equivalence point occurs when the number of H3O1+ equals the number of OH1-. If an indicator is used in a titration, it must change color approximately at the pH of the equivalence point. (The end point is the volume where the indicator changes colors.) If a pH meter is used in a titration, it shows the changes in pH as the acid is slowly added to the base or vise versa.

15.2 A titration graph can be used to determine the molarity of an unknown acid or base.

15.2 A titration graph can be used to determine the molarity of an unknown acid or base. A strong acid with a strong base neutralizes around pH ____. A strong acid with a weak base neutralizes _______________. A weak acid with a strong base neutralizes _______________. A weak acid with a weak base neutralizes ________________.

15.2 A titration graph can be used to determine the molarity of an unknown acid or base. A strong acid with a strong base neutralizes around pH 7 A strong acid with a weak base neutralizes below pH 7. A weak acid with a strong base neutralizes above pH 7. A weak acid with a weak base neutralizes anywhere.

TITRATION GRAPHS The green arrows show equivalence point. The purple arrows show the end point.

15.2 Example 1: Solutions of sodium hydroxide are used to unclog drains. A 43mL volume of sodium hydroxide was titrated with 32.0mL of 0.100M HCl. What is the molarity of the sodium hydroxide?

15.2 Example 2: A volume of 25mL of 0.120M sulfuric acid neutralizes 40mL of a sodium hydroxide solution. What is the concentration of the sodium hydroxide solution?

15.2 Example 3: A titration was performed on 40.0mL of a solution of aniline. The acid/base ratio is 1:1. The following data was collected: Sketch a titration graph Identify the equivalence point. Is aniline an acid or base? Why did the pH change only slightly between 20 and 30 mL of added acid? What is the concentration of the aniline solution? From p. 513, what is the best indicator to use?

15.2

CHAPTER 15 TEST 15 multiple choice (4 points each) 10 short answer (2 points each) 5 short answer (4 points each) 1 extra credit (4 points)

CHAPTER 15 TEST pH scale finding pH or pOH from [H3O+] or [OH-] finding [H3O+] or [OH-] from pH or pOH using Kw to find [H3O+] or [OH-] use [H3O+], pH, pOH, or [OH-] to determine acidity, basicity, or neutrality 2H2O  H3O+ + OH- neutralization reactions (moles of OH- must equal moles of H3O+) strong acid with strong base strong acid with weak base weak acid with strong base titrations finding concentration from data finding concentration from graph deciding on appropriate indicators equivalence point