Chemistry · MU Sofia

3.4. Equilibrium

Covers the Van't Hoff reaction isotherm, linking free energy change to the equilibrium constant and predicting reaction direction, then Le Chatelier-Brown principle with the effects of temperature, concentration and pressure on equilibria. It goes on to conjugated reactions in biochemistry and macroergic bonds, including ATP and creatine phosphate, and closes with a summary of key formulas such as the Van't Hoff equation for temperature effects.

Inside: 13 sections · 9 labelled pictures · 21 flashcards · 6 min

Topic 11 of 42 in the MU Sofia syllabus for Chemistry (Medicine, Year 1). The free AceMed note covers it in 13 sections, about 687 words (6 min of reading), with 21 flashcards.

In this note

  1. Van't Hoff Reaction Isotherm:
  2. Le Chatelier - Brown principle
  3. 1. Influence of Temperature on Equilibrium:
  4. 2. Influence of Concentration on Equilibrium:
  5. 3. Influence of Pressure on Equilibrium:
  6. Conjugation Reactions in Biochemistry:
  7. Compounds with "Macroergic" Bonds:
  8. High-Yield Formulas & Relations (Chemical Equilibrium & Bioenergetics)
  9. Equilibrium Constants
  10. Reaction Quotient (Q)
  11. Relation between Gibbs Free Energy & Equilibrium
  12. Van’t Hoff Equation (Effect of Temperature)
  13. ATP Hydrolysis (Biological Energy Currency)

Van't Hoff Reaction Isotherm:

1. Definitions:

  • Equilibrium constant (Keq): Constant value at equilibrium that represents the ratio of product concentrations to reactant concentrations.
  • Apparent equilibrium constant (Kapp): Value similar to Keq but calculated for a non-equilibrium state.
  • Change in free energy (∆G): Thermodynamic parameter indicating the potential for a reaction to occur.
  • Standard change in free energy (∆G⁰): ∆G under standard conditions (specific temperature and pressure).

2. Relationship between ∆G and Equilibrium:

  • ∆G = ∆G⁰ + RT ln(Keq) (where R is the gas constant and T is temperature).
  • Negative ∆G: Reaction proceeds forward (products favored).
  • Positive ∆G: Reaction proceeds backward (reactants favored).
  • Zero ∆G: System is at equilibrium.

3. Predicting Equilibrium Direction:

  • By comparing ∆G⁰ and ∆Gapp, you can predict the direction of the reaction:
  • ∆G < 0: Reaction proceeds forward to reach equilibrium.
  • ∆G > 0: Reaction proceeds backward to reach equilibrium.

4. External factors and Equilibrium:

  • Changing external factors (temperature, pressure, etc.) can disrupt equilibrium.
  • The system responds by shifting the reaction in a direction that counteracts the change and restores equilibrium.

5. Conclusion:

  • The Van't Hoff reaction isotherm relates the change in free energy to the equilibrium constant, allowing you to predict the direction of a reaction and understand how external factors influence equilibrium.

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