Module 2 chemistry

• Rate of Reaction


  Change in amount (concentration or volume) of chemical (reactant x or product y) over time (seconds, minutes, hours, etc.)

  
• Determining Reaction Rate Experimentally

  1. Overall (complete reaction)

  2. Cross-sectionally (at specific intervals, involves sampling)
• Sampling Method


  Removing small samples from reaction mixture and further disrupting, pausing, or quenching any further reaction
• Collision Theory


  • More frequent and effective collisions lead to greater product formation
• Factors influencing Reaction Rate

  • Concentration
  • Pressure
  • Size
  • Temperature
  • Catalyst
• Activation Energy (Ea)


  Minimum input required to initiate a reaction between colliding particles, depends on type of reaction (endothermic vs exothermic)
• Activation Energy


  Reaction 1 requires less than Reaction 2

  
• Activation Energy


  Reaction 1 takes place at a lower temperature than Reaction 2

  
• Boltzmann (Distribution) Curve


  Area under the curve represents the number of particles with a given energy
• Boltzmann Curve


  As temperature increases, the curve shifts to the right
• Activation Energy, Boltzmann Curve, Catalysis

  Catalysts lower the activation energy, shifting the Boltzmann curve to the left
• In the industrial production of ammonia, the highest yield is achieved at high temperature and pressure
• Catalysts are used in the industrial production of ammonia
• Methods to assess/monitor Reaction Rates

  • Gases generated
  • Colour change
  • Electric conductivity
  • pH change
  • Weight
  • Radioactive emissions
• Measuring Reaction Rate using Gas Generation

  1. Write reaction equation

  2. Identify gas produced

  3. Measure volume of gas over time
• Order of Reaction


  Relationship between rate of reaction and concentration of participating species, represented by power in rate equation
• Order of Reaction Examples

  • First order: Rate = k[A]
  • Second order: Rate = k[A]^2
  • Zero order: Rate = k

  
• Order of reaction cannot be determined exclusively via stoichiometric processes

  
• Order of reaction is deduced from experimentally determined rate equations
• Graphical methods can be used to determine order of reaction
• Rate Constant (k)


  Units determined by order of reaction, can be deduced mathematically or experimentally
• Half-Life (t1/2)


  Time taken for amount/concentration of a substance to be reduced to half its initial/previous value
• Calculating Half-Life and Concentration of Radioactive Isotope

  1. Calculate half-life from decay curve

  2. Calculate concentration at a given time using initial concentration and half-life

  3. Calculate rate constant k

  
• Figure 7.1.1 The reaction of calcium carbonate with hydrochloric acid can be found by measuring the volume of carbon dioxide given off
• Rate of reaction


  Can be determined experimentally
• OVERALL, the complete reaction

  1. Rate=

  2. final - til
• CROSS-SECTIONALLY (La specifier). This wolves sampling method

  1. Rate=

  2. x2-x1

  3. t2 — t1
• When analysing markets, a range of assumptions are made about the rationality of economic agents involved in the transactions
• AIMS | OBJECTIVES


  • Recall recent critical concepts and related calculations
  • Discuss details of Bronsted-Lowry Acid-Base Theory
  • Acid and Base dissociation constants (Ka and Kb respectively)
  • Calculating pH and pOH
  • Acid-Base reaction Indicators

  
• Le Chatelier's Principle


  if/when equilibrium is disturbed (by a change in conditions) the position of equilibrium shifts to as to re-equilibrate
• Changes that can disturb equilibrium

  • concentration
  • pressure
  • temperature
• Le Chatelier's Principle: ...concentration

  1. Increasing the concentration of the "reagents" shifts the equilibrium toward the right (i.e. more "products" being formed)

  2. Increasing the concentration of the "products" shifts the equilibrium toward the left (i.e. more "reagents" being formed)
• change in concentration does not impact Kc or Kp
• Le Chatelier's Principle: ...pressure

  1. Increasing the pressure of the system shifts the equilibrium toward the right (i.e. more "products" being formed)

  2. Decreasing the pressure of the system shifts the equilibrium toward the left, as there is less space between molecules (i.e. more "reagents" being formed)
• equilibration only occurs if the number of gas molecules on the right are different from those on the left, i.e. a + b ≠ c
• Le Chatelier's Principle: ...temperature

  1. Increase (△T): Endothermic - Equilibrium shifts toward the right (i.e. more "products" being formed), Kc and Kp increases

  2. Increase (△T): Exothermic - Equilibrium shifts toward the left (i.e. more "reagents" being formed), Kc and Kp decreases

  3. Decrease (▽T): Endothermic - Equilibrium shifts toward the left (i.e. more "reagents" being formed), Kc and Kp decreases

  4. Decrease (▽T): Exothermic - Equilibrium shifts toward the right (i.e. more "products" being formed), Kc and Kp increases

  
• change in temperature impacts both Kc or Kp
• Solubility product constant Ksp

  When raising the ions to the power of their relative concentrations, experimenters must consider the ion ratio
• ion ratio = mA/nB
• Common Ion Effect


  The decrease/reduction in solubility of an ionic precipitate by the addition to the solution of a soluble compound with an ion in common with the precipitate