Volumetric Analysis: Acid-Base & Redox Titrations

Understanding Titrations

Titration is a technique used in chemistry to determine the concentration of an unknown solution by reacting it with a solution of known concentration. There are two main types of titrations:

• Acid-Base Titrations: Involves the reaction between an acid and a base.
• Redox Titrations: Involves a reduction-oxidation reaction between the titrant and the analyte.

Acid-Base Titrations

In acid-base titrations, the concentration of an acid or base is determined by neutralizing it with a base or acid of known concentration. The point at which neutralization occurs is called the equivalence point.

Steps in Acid-Base Titration

1. Prepare the solutions: Fill the burette with the titrant (known concentration) and the flask with the analyte (unknown concentration).
2. Add indicator: Use an appropriate indicator that changes color at the equivalence point.
3. Titrate: Slowly add the titrant to the analyte while stirring until the indicator changes color.
4. Calculate concentration: Use the volume of titrant added to calculate the concentration of the analyte.

Calculating Percentage Purity

The percentage purity of a substance in a sample can be determined using titration data. The formula is:

$$\text{Percentage Purity} = \left( \frac{\text{Mass of Pure Substance}}{\text{Total Mass of Sample}} \right) \times 100$$

Redox Titrations

Redox titrations involve the transfer of electrons between the titrant and the analyte. Common examples include the titration of iron(II) ions with potassium permanganate.

Example of Redox Titration

Titrating iron(II) sulfate with potassium permanganate:

• Balanced equation: $$\text{MnO}_4^- + 5\text{Fe}^{2+} + 8\text{H}^+ \rightarrow \text{Mn}^{2+} + 5\text{Fe}^{3+} + 4\text{H}_2\text{O}$$
• Use the stoichiometry of the reaction to calculate the concentration of the unknown solution.