Acid-Base Titration & pH Chapter 15

1. Acid-Base Titration & pHChapter 15 West Valley High School General Chemistry Mr. Mata

2. Standard 5e • Students will know how to conduct an acid-base titration using a standard solution, an indicator, and an unknown solution.

3. Essential Question: • How is titration used to determine the molarity of an unknown acid or base?

4. Acid –BaseTitration • Titration = method to determine the concentration of an unknown acid or base. • Standard solution = solution of known molarity. • Endpoint = point at which neutralization occurs. • Endpoint usually shown by color change of an acid - base indicator.

5. Indicators • Indicators • compounds that change their color in the presence of acids or bases. • Indicators appear to change color when placed in different concentrations of acids and bases. • Phenolphthalein • colorless in the presence of an acid and magenta in the presence of a base. • Universal Indicator • displays a spectrum of colors, depending upon acid and base concentration.

6. Indicator Use • Some indicators are better suited to different acid/base reactions. • Transition interval • the range of pH that they are effective. • End point • point where indicator changes from one color to another. • mole H+= moles OH-(endpoint = 7)

7. Titrations • Titrations allow us to analytically determine an acid or base concentration (M). • Titrations are far more precise than indicators. • Titrations are performed by adding a known amount of a known-concentration acid to an unknown base or… • Adding a known amount of a known-concentration base to an unknown acid.

8. Titration Curves • Titration curves can show how pH of a titration (acid-base solution) changes as one compound is added to the other. • The equivalence point is the point at which: • mole acid = mole base

9. Buret Used in Acid-Base Titrations