Chemistry Chapter on Titration and Solutions

Standard Solutions

• A reagent of known concentration, stable and reactive
• Prepared by dissolving accurate weight of pure reagent in water and diluting to known volume
• Concentration determined by dissolving pure reagent in water and diluting to exact volume

Titrated Solutions

• Solutions with approximate concentration
• Prepared from unstable or reactive materials
• Exact concentration is determined by titration with a standard solution

Neutralization Titration

• Method involving a reaction between an acid and a base resulting in a neutral solution at pH 7 (for strong acid-strong base reactions)
• Equivalence point: The point where reactants have completely reacted with no excess.
• At the equivalence point: Cn1 * V1 = Cn2 * V2 where Cn represents normality and V represents volume.

Concentration Calculation

• Concentration (normality, Cn) can be calculated by the equation Cn= m / E*V where m is the solute mass, E is the equivalent weight, and V is the solution volume
• Neutralization titration: reaction between an acid and a base which produces a neutral solution (pH=7)
• The general reaction is: acid+ + base– → salt + water

Titration Curves & Indicators

• Strong acid titrated with strong alkali (e.g., HCl + NaOH → NaCl + H2O)
  • Equivalent point pH=7
  • No hydrolysis of salt
  • Indicator: Methyl Orange
• Strong alkali titrated with strong acid (e.g., 2 NaOH + 2 HCl = 2 NaCl + 2 H2O)
  • Equivalent point pH=7
  • No hydrolysis of salt
  • Indicator: Methyl Orange
• Weak acid titrated with strong alkali (e.g., CH3COOH + NaOH → CH3COONa + H2O)
  • Equivalent point pH>7
  • The salt is hydrolyzed
  • Indicator: Phenolphthalein

Expression of Concentration

• Molarity (M): Number of gram moles of reagent contained in one liter solution (mol/L)
• Normality (N): Number of gram equivalents contained in one liter of solution.
• Percent concentration (C%): Grams of material dissolved in 100 grams of solution
• Titer: Number of solute’s grammes in one cm3 (ml) of the solution (g/cm3 )

Complex Compounds

• The formula of complex ions is out in square brackets, and it is placed at the front if its charge is positive
• The name of complex cations starts with the greek prefix for the coordination number (e.g., mono-, di-, tri-, and etc) followed by the name of the ligand, and the name of the metal ion with valence state indicated

Werner’s Coordination Theory

• Metals in coordination compounds exhibit primary valency (oxidation state) and secondary valency (coordination number)
• These secondary valencies are spatially directed, leading to specific geometries.

Complexometry

• Complexone: Any chelating agent used for the analytical determination of metals
• Chelating agents form stable complex compounds, called complexonates, with numerous ions of metals
• EDTA (ethylene- diammine tetraacetic acid) is commonly used as a complexone
• Trilon B: Salt of EDTA (disodium ethylenediaminetetraacetate)

Water Hardness

• Classified as temporary or permanent
• Temporary Hardness (Carbonate Hardness): Caused by Ca(HCo3)2 and Mg(HCo3)2 dissolved in water
• Permanent Hardness (Non-carbonate Hardness): Mainly caused by Ca2+/ Mg2+ sulfates, chlorides, silicates, phosphates and nitrates.

Water Softening

• Process of removing calcium, magnesium, and sometimes iron ions.

Determining Water Hardness

• Temporary Hardness: Can be removed by boiling and measured by titration
• Permanent Hardness: Found by subtracting temporary hardness from total hardness
• Total Hardness: Measured directly via EDTA titration

Oxidation-Reduction (Redox) Processes

• Reactions involve changes in oxidation numbers, where oxidation is the loss of electrons (increase in oxidation number) and reduction is the gain of electrons (decrease in oxidation number)

Redox Equations

• Redox reactions combine both an oxidation and a reduction into a single reaction

Redoximetry

• Methods are classified based on whether they use oxidizing or reducing agents in titration

Qualitative Analysis

• Irreversible reactions: Proceed to completion, often driven by the formation of products that are insoluble, gaseous, weak electrolytes or complex compounds
• Analytical reactions in electrolyte solutions: Produce distinct observable changes known as analytical signals that include the presence of certain ions
• Flame tests: Detect the presence of certain metal ions based on the color they impart to a flame.

Solutions

• Classified based on particle size and state
• True solutions have particles < 1nm and are homogenous
• Colloids have particles between 1nm and 500nm and are heterogenous
• Suspensions have particles > 500 nm and are heterogenous

True Solutions

• Solubility: Factors related to solubility include temperature, pressure, and the nature of the solute and solvent
• Factors affecting the “rate” of solubility include surface area, stirring, and temperature
• Concentration of solutions: Mass percent solution, Molarity, Molality, Mole fraction

Physical Properties of True Solutions

• Vapor pressure: In a solution, the presence of a non-volatile solute reduces the solvent vapor pressure compared to its pure state
• Raoult’s Law: For ideal solutions, the vapor pressure of the solution (Psolution) is directly proportional to the mole fraction of the solvent (X solvent) in the solution
• Melting point: The melting point of a solution is lower than the melting point of the pure solvent
• Boiling point: The boiling point of a solution is higher than the boiling point of the pure solvent
• Osmotic pressure: The pressure that needs to be applied to a solution to prevent the inward flow of water across a semipermeable membrane.

Test your knowledge on standard solutions, titrated solutions, and the principles of neutralization titration. This quiz covers concepts like concentration calculations and the equivalence point in titrations. Enhance your understanding of these essential chemistry topics.