Acid-Base Titration & pH Chapter 15 West Valley High School General Chemistry Mr. Mata

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

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

Acid – Base Titration 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.

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

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

Titrations Titrations MTitrations allow us to analytically determine an acid or base concentration (M). –Titrations are far more precise than indicators. known amount of a known-concentration acid unknown baseTitrations are performed by adding a known amount of a known-concentration acid to an unknown base or… known amount of a known- concentration baseunknown acidAdding a known amount of a known- concentration base to an unknown acid.

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

Buret Used in Acid-Base Titrations