Solutions and Stoichiometry

Ionic and Polar Solutions

• Definition of Solutions: A solution is formed when a solute dissolves in a solvent, producing a homogeneous mixture.

• Properties of Solutions:

  • Particles are smaller than 1 nm in size.

  • Cannot be separated by simple filtration.

  • The solute 'gets dissolved' (e.g., sugar in water).

  • The solvent 'does the dissolving' (e.g., water dissolves sugar).

Solvation Process

• Solvation: Interaction between solvent and dissolved solute leading to dissolution.

  • Specific term for water as the solvent is called hydration.

  • Dissolution relies on mutual attraction between solute and solvent particles.

• Example: Diagram shows solvation of salt (NaCl) in water (H₂O).

Dissolving, Dissociating, and Ionizing

• Dissolving:

  • Separating a substance into individual particles.

• Dissociation:

  • Ionic substances separate into their component ions.

• Ionization:

  • Forms ions from a substance that initially does not exist as ions in solution.

• Electrolytes: Solutions that can conduct electricity due to presence of ions.

Polarity and Solubility

• Polarity: Distribution of electrons in a molecule.

  • Polar molecules: Unequal electron distribution.

  • Nonpolar molecules: Equal electron distribution.

• Dissolution Principle: "Like dissolves like"

  • Polar substances dissolve in polar solvents; nonpolar substances dissolve in nonpolar solvents.

• Miscibility: A substance's ability to dissolve in another.

  • Miscible: Can dissolve

  • Immiscible: Cannot dissolve.

Solution Concentration

• Types of Solutions:

  1. Unsaturated: Can dissolve more solute.

  2. Saturated: Cannot dissolve more solute.

  3. Supersaturated: Contains more solute than maximum solubility, unstable (may crystallize).

• Concentration: Amount of solute in solution.

Molarity (M)

• Definition: Number of moles of solute per liter of solution.

  • Higher molarity indicates a higher solute concentration.

• Molarity Calculation:

  • M = moles of solute / liters of solution

  • M = total grams of solute / (molar mass 00 mL of solution)*

Molarity Calculations

• Example 1: Molarity of a 2.5 L solution with 1.25 moles of KCl:

  • M = 1.25 mol / 2.5 L = 0.50 M KCl

• Example 2: Calculating molarity from moles and volume. Beaker A (0.06 moles in 0.06 L): 1 M; Beaker B (0.18 moles in 0.06 L): 3 M

  • More Concentrated: Beaker B.

Solution Stoichiometry

• Utilizing molarity as a conversion factor in stoichiometry calculations.

  • Conversion formula: Molarity = moles of solute / L of solution

• Stoichiometric relationships can be derived based on mole ratios from balanced equations.

Acids and Bases

• Definitions:

  • Acids: Produce hydrogen ions (H⁺) when dissolved.

  • Bases: Produce hydroxide ions (OH⁻) in solution.

  • Neutral: Equal concentrations of H⁺ and OH⁻.

• pH Scale: Measure of acidity/basicity:

  • pH < 7: Acidic

  • pH = 7: Neutral

  • pH > 7: Basic

Bronsted-Lowry Definitions

• Acid: Produces H₃O⁺ when donating H⁺ to water.

• Base: Accepts H⁺ ions.

• Diagram illustrates ionization of HCl and NaOH in water.

Neutralization Reactions

• General Reaction:

  • Acid + Base → Salt + Water

  • Example reactions show various neutralization processes.

The Auto-Ionization of Water

• Water can auto-ionize:

  • H₂O ↔ H₃O⁺ + OH⁻

• Ionization Constant (Kw): K w = [H₃O⁺][OH⁻]

  • At 25°C, Kw = 1.00 × 10⁻¹⁴

Preparing Solutions

• Dilution: Adding solvent to a solution reduces molarity but keeps moles of solute constant.

• Dilution Formula: M₁V₁ = M₂V₂

Titrations

• Technique to determine the concentration of an unknown acid/base.

• Equivalence Point: Moles of acid = moles of base.

• Important formula for calculations: (M₁V₁ = M₂V₂)

Strength of Acids and Bases

• Strong Acids: Completely dissociate (e.g. HCl).

• Weak Acids: Partially dissociate (e.g. HCOOH).

• Eight Strong Acids:

  1. HCl - Hydrochloric Acid

  2. HBr - Hydrobromic Acid

  3. HI - Hydroiodic Acid

  4. HNO₃ - Nitric Acid

  5. H₂SO₄ - Sulfuric Acid

  6. HCIO₄ - Perchloric Acid

  7. LI OH - Lithium Hydroxide

  8. NaOH - Sodium Hydroxide

Pathways for Acid-Base Calculations

• Emphasizing stoichiometry for calculating molarity, volume, and concentrations regarding tittrations and reactions in general.