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

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 concentration (molarity). Endpoint = point at which neutralization occurs. Endpoint usually shown by color change of an acid-base indicator.

Indicators Indicators compounds that change their molecular configuration 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.

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)

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.

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

Buret Used in Acid-Base Titrations