Lecture 18.2a- Equilibrium

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Section 18.2 (part A) lecture for Honors & Prep Chemistry

Section 18.2 (part A) lecture for Honors & Prep Chemistry

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  • 1. Bellwork- collision theory Explain, using collision theory, WHY the following factors increase reaction rate. a. Increase temperature b. Increase surface area c. Increase reactant concentrations d. Add a catalyst
  • 2. At chemical equilibrium, no change occurs in the amounts of the products and reactants. At equilibrium the system is stable H2O(s) ⇌ H2O(l) equilibrium at 0°C Means the process is at equilibrium
  • 3. A reversible reaction is one in which the conversion of reactants to products and the conversion of products to reactants occur simultaneously. forward 2SO2 + O2 ⇌ 2SO3 reverse 2SO3 ⇌ 2SO2 + O2
  • 4. 2SO2 + O2 ⇌ 2SO3 There are 6 mol SO2 and 3 mol O2 in a closed container As the reaction progresses, reactants form products. The forward reaction rate SLOWS as reactant concentration decreases. The reverse reaction rate INCREASES as product concentration increases.
  • 5. 2SO2 + O2 ⇌ 2SO3
  • 6. 2SO2 + O2 ⇌ 2SO3
  • 7. When the rates of the forward and reverse reactions are equal, the reaction has reached a state of balance called chemical equilibrium.
  • 8. At equilibrium the concentrations of all “species” are constant. Equilibrium position = the specific concentrations of all species at equilibrium, which can be calculated for any reaction.
  • 9. SO2 and O2 SO3 react to give decomposes SO3 to SO2 and O2 At equilibrium, all three types of molecules are present.
  • 10. If the rate of the shoppers going up the escalator is equal to the rate of the shoppers going down, then the number of shoppers on each floor remains constant, and there is an equilibrium.
  • 11. In order to reach equilibrium you need A closed container Stable temperature Low activation energies
  • 12. The equilibrium constant (Keq) is a ratio of product concentrations to reactant concentrations at equilibrium. For aA + bB  cC + dD Coefficients Keq = [C]c[D]d become [A]a [B]b exponents!
  • 13. A value of Keq greater than 1 means that products are favored over reactants; A value of Keq less than 1 means that reactants are favored over products. products =K reactants
  • 14. 18.2 Section Quiz. 1. In a reaction at equilibrium, reactants and products a) decrease in concentration. b) form at equal rates. c) have equal concentrations. d) have stopped reacting.