Titration  Lab technique commonly utilized to determine an UNKNOWN concentration of a chemical compound with a KNOWN concentration of another chemical compound.  Chemical compounds combine with exact stoichiometric proportions  Analyte—  Chemical compound with unknown concentration  Titrant—  Chemical compound with known concentration  Measured with volume and concentration  Added to chemical compound with unknown concentration in titration

Acid-Base TitrationAcid-Base Titration  Technique used to perform a neutralization reaction  Acid/Base with KNOWN concentration used to determine acid/base with UNKNOWN concentration  Neutralization Reaction:  Acid + Base  Salt + H 2 O

Titration TerminologyTitration Terminology  End Point :  point in a titration where a color change is observed due to indicator.  Equivalence Point :  point during a titration when neutralization has occurred.  Equal amount of acid and base  Cannot usually be observed  We can plot a titration on a graph— titration curve **Ideally, equivalence point = endpoint **

2 Types of Acid-Base Titrations 1)Strong Acid/Strong Base Titrations 2)Weak Acid/Strong Base Titrations

1. Strong Acid/Strong Base Titrations  Low initial pH value  Sharp increase in pH before equivalence point  Equivalence point is pH = 7  Rapid pH increase after equivalence point **Indicators with pH range 4-10 helpful for these titrations **Neutralization reactions

Strong Acid with Strong Base Titrant Strong Base with Strong Acid Titrant

Example 1: Strong Acid/Strong Base Titration Calculations  30 ml of 0.50M HCl is titrated with 0.50M NaOH. a) Find the pH of 0.50M HCl

Example 1: Strong Acid/Strong Base Titration Calculations  30 ml of 0.50M HCl is titrated with 0.50M NaOH. b) Find the pH after 15 ml of NaOH added

Example 1: Strong Acid/Strong Base Titration Calculations  30 ml of 0.50M HCl is titrated with 0.50M NaOH. c) Find the pH after 30 ml of NaOH added

Example 1: Strong Acid/Strong Base Titration Calculations  30 ml of 0.50M HCl is titrated with 0.50M NaOH. d) Find the pH after 45 ml of titrant added

2. Weak Acid/Strong Base Titrations  High initial pH value  pH = pKa at half-neutralization  [weak acid] = [conjugate base]  Ka = [H 3 O + ] [A - ] SO Ka = [A - ]/[HA] is 1:1 [HA]  Ka = [H 3 O + ], SO pH = pKa

2. Weak Acid/Strong Base Titrations  Equivalence point > 7 on pH scale **Indicators with pH range > 7 helpful as pH equivalence point is basic

Homework  p. 671 #97  p. 673 #117