South Pasadena AP Chemistry Name _________________________________ Period ___ Date ___/___/___ 18 Acid-Base Reactions T I T R A T I O N C U R V E C A L C U L A T I O N S Strong Acid – Strong Base Titrations When a strong acid (such as HCl) and a strong base (such as NaOH) are used for a titration, the pH change looks like the graph on the right. You can calculate the volume of base needed to reach the equivalence point using the formula: V·M = V·M or a line equation. There are three situations in which you determine pH. initial strong acid concentration (this is simply the –log[H + ] which is based on the [Acid].) equivalence point (or endpoint) when moles of OH = moles of H + . The pH is 7 (due to the auto-ionization of water.) before and after the endpoint (calculate excess moles of H + or OH - , divide by the total volume, and calculate the pH based on this value.) Weak Acid – Strong Base Titrations When a weak acid (such as HC 2 H 3 O 2 ) is neutralized by a strong base (such as NaOH), the graph varies in two ways: the equivalence point is
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