test 1 revision

• Rate of reaction


  How quickly a chemical reaction occurs, typically measured by how fast reactants are consumed or products are formed per unit of time
• Factors affecting reaction rates

  • Concentration of reactants
  • Temperature
  • Surface area
  • Catalysts
  • Pressure (for gases)
  • Nature of reactants
• Concentration of reactants


  Increasing the concentration of reactants generally increases the rate of reaction, as higher concentration means more collisions between reactant molecules, leading to a higher chance of effective collisions
• Temperature


  Higher temperature usually increases the rate of reaction, as higher temperatures mean reactant molecules move faster, leading to more frequent and energetic collisions
• Surface area


  In reactions involving solids, increasing the surface area of the solid reactants increases the rate of reaction, as more surface area exposes more reactant particles to potential collisions
• Catalysts


  Substances that increase the rate of reaction without being consumed in the reaction, by providing an alternative reaction pathway with lower activation energy
• Pressure (for gases)


  Increasing pressure for gaseous reactions can increase the rate of reaction, as higher pressure leads to higher concentration of gas particles, thus increasing the frequency of collisions
• Collision theory


  Explains how reactions occur and why reaction rates vary, stating that for a reaction to occur, reactant particles must collide with sufficient energy and proper orientation
• Activation energy


  The minimum energy required for a reaction to occur, with reactions having higher activation energies tending to be slower
• Chemical equilibrium


  Occurs in a reversible reaction when the rate of the forward reaction equals the rate of the reverse reaction, resulting in constant concentrations of reactants and products over time
• Characteristics of equilibrium


  • Dynamic equilibrium
  • Reversible reactions
  • Constant concentrations
• Le Chatelier's Principle


  States that if a system at equilibrium is subjected to a stress, it will adjust to relieve that stress and restore equilibrium
• Factors affecting equilibrium


  • Concentration changes
  • Pressure changes (for gaseous reactions)
  • Temperature changes
  • Catalysts
• Equilibrium constant (Kc)


  The ratio of product concentrations to reactant concentrations at equilibrium, expressed using the law of mass action, indicating the extent to which the reaction proceeds towards products or reactants
• pH


  A measure of the concentration of hydrogen ions (H⁺) in a solution, defined as the negative logarithm of the hydrogen ion concentration
• pOH


  A measure of the concentration of hydroxide ions (OH⁻) in a solution, defined as the negative logarithm of the hydroxide ion concentration
• pH + pOH = 14 (for aqueous solutions at 25°C)
• Buffer solutions


  Solutions that resist changes in pH upon addition of small amounts of acid or base, typically consisting of a weak acid and its conjugate base, or a weak base and its conjugate acid
• Definitions of acids and bases

  • Arrhenius theory: Acids ionize in water to produce hydrogen ions (H⁺), bases ionize in water to produce hydroxide ions (OH⁻)
  • Brønsted-Lowry theory: Acids donate protons (H⁺), bases accept protons
• Neutralization reactions


  Occur between an acid and a base to produce salt and water
• Strengths of acids and bases

  • Strong acids: Completely ionize in water (e.g. HCl, H₂SO₄, HNO₃)
  • Weak acids: Partially ionize in water (e.g. CH₃COOH, H₂CO₃)
  • Strong bases: Completely dissociate into metal ions and hydroxide ions in water (e.g. NaOH, KOH)
  • Weak bases: Partially ionize in water (e.g. NH₃, RNH₂)
• Ionization of water


  Water undergoes autoionization to form H⁺ and OH⁻ ions, with the concentration of H⁺ ions equal to the concentration of OH⁻ ions in pure water at 25°C (1.0 × 10⁻⁷ M)
• Acidic, basic, and neutral solutions

  Solutions with pH less than 7 are acidic, solutions with pH greater than 7 are basic, solutions with pH of 7 are neutral
• Buffer solutions


  Resist changes in pH upon addition of small amounts of acid or base, consisting of a weak acid and its conjugate base, or a weak base and its conjugate acid, with buffer capacity depending on the concentrations of the weak acid/base and its conjugate pair
• Common acid-base indicators


  • Litmus, phenolphthalein, methyl orange, bromothymol blue