Analytical Chemistry: Titration and Neutralization

Neutralization Reactions and Acid-Base Titration

• Neutralization reactions involve the formation of slightly ionized or slightly soluble products.
• Acid-base titration is a method to determine the concentration of an unknown acid using a known base.
• A buret measures the base's volume.
• The acid's concentration is unknown.

Analytical Chemistry

• Analytical chemistry involves qualitative and quantitative analysis.
• Qualitative analysis identifies the constituents of a compound or mixture.
• Quantitative analysis determines the quantity and purity of a sample.
• Different methods classify quantitative analysis on the types of sample concentration, analyzed material, and final measurement process.

Methods Used in Quantitative Analysis

• Sample concentration can be macro (100 mg+), semi-micro (10-100mg), and micro (less than 1 mg)
• Material type determines the necessary analysis, e.g., food, water analysis.
• Measurement methods include volumetric or titrimetric analysis, gravimetric analysis, and physicochemical or instrumental methods

Classification of Quantitative Analysis Methods

• Volumetric or titrimetric analysis involves measuring the volume of a known concentration reagent called the titrant, needed for complete reaction with the analyzed sample, called the titrand
• Gravimetric analysis involves isolating and weighing a final product that has a known, pure, stable, and definite chemical structure
• Physicochemical or instrumental methods measure physical properties related to the concentration of the constituent to be analyzed, employing specific instruments.

Volumetric or Titrimetric Analysis

• It's based on measuring the volume of both the analyzed sample and the standard solution required for complete reaction.
• Titration is the measurement of a sample's ability to combine with a known standard reagent in a quantitative manner.
• "Titrant" is the compound in the buret; its concentration is known.
• "Titrand" is the substance being analyzed.

Gravimetric Analysis

• Measuring the weight of a final product (with a known, pure, stable, and definite chemical structure) after isolating it
• Involves processes like weighing a sample, adding a precipitating agent, heating, filtering, drying, and weighing the precipitate

Physicochemical or Instrumental Methods of Analysis

• Measuring physical properties related to the concentration of the constituent being analyzed using specific instruments
• This is why it's called instrumental analysis

Requirements of Titrimetric Reactions

• Reaction must be easily expressed through a chemical equation.
• Only one reaction should occur between the titrant and sample, with no side reactions.
• The reaction should be instantaneous, or a catalyst should be used.
• A suitable standard solution should be available as the titrant.
• The reaction's endpoint should be easily detected. This could be by detecting physical or chemical changes or through chemical indicators.

Standard Solutions

• Solutions with exactly known chemical composition and concentration
• Molar Solutions contain one gram molecular weight per liter

Preparation of Standard Solutions

• Direct Methods: Accurately weighed primary standards are dissolved and added to a volumetric flask, to the required volume.
• Indirect Methods: If a compound isn't a primary standard, it can be used to create a solution with an approximate concentration. This solution is standardized against a primary standard solution.

Characteristics of Primary Standards

• Easily obtained in high purity (known as "AR").
• Easily tested for impurities.
• Stable and non-hygroscopic.
• Non-volatile and can be dried at specific temperatures without decomposition.
• Reacts stoichiometrically.
• Readily soluble in the solvent used.
• High equivalent weights help minimize weighing errors

Examples of Primary Standards (Acid-base reactions)

• Potassium acid phthalate
• Constant boiling point HCl
• Anhydrous Na₂CO₃
• Benzoic acid
• Mercuric oxide
• Potassium bicarbonate

Examples of Primary Standards (other reaction types)

• Complex formation: Ag, AgNO₃, various metals (Zn, Mg, Cu, Mn) and their salts.
• Precipitation: Ag, AgNO₃, NaCl, KCl, KBr.
• Oxidation-reduction: K₂Cr₂O₇, KBrO₃, KIO₃, KH(IO₃)₂), Na₂C₂O₄, As₂O₃