1. Titrations

2. Standard Solution Sample Solution Burette A titration is a volumetric analysis technique used to find the [unknown] of a sample solution by adding a standard solution of [known] and volume

3. A sufficient amount of standard solution is added until equal moles of each have reacted or the equivalence point has been reached.

4. A common titration involves an acid-base neutralisation reaction. One of the reactants must be either a strong acid or base or both (must go to completion) as follows: ACID + BASE  WATER + SALT Titrations do not always yield an equivalence point with a pH of 7. Why? –The salt can alter the final pH of the solution.

5. Depends on the strength of the reacting acids/bases: An indicator must be chosen to signal the equivalence point of a titration. It does this by a change in colour at the equivalence point.

6. Choosing Indicators For Titrations will depend on the overall pH of the salt produced yellowblue

8. Strong Acids and Strong Base Titrations Example: HCl (strong acid) and NaOH (strong base) Formula Equation:__________________________________ Complete Ionic Equation: ____________________________ Net Ionic Equation:__________________________________ pH at equivalence point: _____________________________ Possible Indicators:__________________________________ HCl + NaOH  H 2 O + NaCl H + + Cl - + Na + + OH -  H 2 O + Na + + Cl - H + + OH -  H 2 O pH = 7 (neutral salt) Bromothymol blue

9. Titration Curve for Strong Acid & Strong Base pH of sample solution is very low  SA Base is being added; pH increases

10. Example: CH 3 COOH (weak acid) and NaOH (strong base) pH at equivalence point: _____________________________ Possible Indicators:__________________________________ Weak Acids and Strong Base Titrations

11. Weak Acid & Strong Base pH starts higher as CH 3 COOH is a weaker acid E.P > 7

12. Weak Base and Strong Acid Titrations Example: NH 3 (weak base) and HCl (strong acid) pH at equivalence point: _____________________________ Possible Indicators:__________________________________

13. Weak Base & Strong Acid Standard Acid is added Sample of Strong Base E.P < 7

14. Example: A 25.00mL sample of HCl was titrated with a standard NaOH solution of concentration 0.0100molL -1. If 32.45mL of base was needed to reach the EP, what was the concentration of the HCl?