Analytical Chemistry Section 3 Study Notes

Study Notes

Analytical Chemistry Section 3 - Study Notes

Neutralization Reactions (Acid-Base Titration): A chemical reaction between an acid and a base, producing a salt and water. Used in volumetric analysis.
pH Indicators: Substances that change color depending on the pH of a solution. This change signals the endpoint of a titration.
- Phenolphthalein: Colorless in acidic solutions, pink in basic solutions.
- Methyl Orange: Red in acidic solutions, yellow in basic solutions.
Standard Solutions: Solutions with precisely known concentrations, crucial for volumetric analysis.
Types of Standard Solutions:
- Primary Standard: A highly pure compound used to prepare standard solutions. Characteristics include high purity, stability in air and solution, non-hygroscopic, inexpensive, large formula weight, and solubility in various solvents. Primary standards react rapidly and completely with the analyte and have long-term stability (e.g., sodium carbonate).
- Secondary Standard: A solution standardized using a primary standard. Used when a primary standard is unavailable or difficult to obtain. It must be standardized against a known standard solution to guarantee an accurate concentration.
Acid-Base Titration: A method to determine the concentration of an unknown acid or base using a standard solution of known concentration.
- Aqueous Titration: Acid-base titrations performed in aqueous solutions.
- Non-aqueous Titration: Acid-base titrations not performed in aqueous solutions.
Preparation of 0.1N HCl (36.46): Procedure for preparing a 0.1 normal hydrochloric acid solution includes adding 5mL of concentrated HCl to 200 mL of distilled water in a 500 mL conical flask, and then bringing the solution to the mark with distilled water.
Standardization with 0.1N Na₂CO₃ (M.Wt= 106): Procedure to prepare a primary standard sodium carbonate solution involves dissolving 1.325 g of Na₂CO₃ in a small beaker, then transferring it into a 250 mL conical flask and diluting to the mark with distilled water.
Titration Procedure:
- 10 mL of the sample (primary standard solution) is placed in a conical flask
- 2-3 drops of methyl orange indicator are added
- Titrate with 0.1N HCl
- Endpoint: The color change from yellow to red indicates the endpoint of the titration.
- Calculation: N₁V₁ = N₂V₂ (Normality 1 * Volume 1= Normality 2 * Volume 2) is used to determine the concentration.
Standardization Factor (f): A factor that corrects for the approximate concentration of a standard solution. Its value ranges from 0.95 to 1.05. Calculated by dividing the volume of the exact standard solution by the volume of the approximate standard solution.