1 / 13

Equilibrium

Equilibrium. Topic 7. 7.2.1 THE EQUILIBRIUM CONSTANT ( K c or K). For any type of chemical equilibrium of the type a A + b B  c C + d D the following is a CONSTANT (at a given T).

lester
Download Presentation

Equilibrium

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Equilibrium Topic 7

  2. 7.2.1 THE EQUILIBRIUM CONSTANT (Kc or K) For any type of chemical equilibrium of the type a A + b B c C + d D the following is a CONSTANT (at a given T) If Kc is known, then we can predict concs. of products or reactants.

  3. Determining Kc 2 NOCl(g)  2 NO(g) + Cl2(g) [NOCl] [NO] [Cl2] Initial 2.00 0 0 Change -0.66 +0.66 +0.33 Equilibrium 1.34 0.66 0.33

  4. Chemical Equilibrium from the labFe3+ + SCN- FeSCN2+ • After a period of time, the concentrations of reactants and products are constant. • The forward and reverse reactions continue after equilibrium is attained.

  5. Writing and Manipulating K Expressions Solids and liquids NEVER appear in equilibrium expressions. S(s) + O2(g)  SO2(g)

  6. Writing and Manipulating K Expressions Solids and liquids NEVER appear in equilibrium expressions. NH3(aq) + H2O(liq)  NH4+(aq) + OH-(aq)

  7. The Meaning of K 1. Can tell if a reaction is product-favored or reactant-favored. For N2(g) + 3 H2(g)  2 NH3(g) Conc. of products is much greater than that of reactants at equilibrium. The reaction is strongly product-favored.

  8. The Meaning of K For AgCl(s)  Ag+(aq) + Cl-(aq) Kc = [Ag+] [Cl-] = 1.8 x 10-5 Conc. of products is much less than that of reactants at equilibrium. The reaction with small K is strongly reactant-favored. Ag+(aq) + Cl-(aq) AgCl(s) is product-favored.

  9. Product- or Reactant Favored Product-favored K > 1 Reactant-favored K < 1

  10. EQUILIBRIUM AND EXTERNAL EFFECTS • Temperature, catalysts, and changes in concentration affect equilibria. • The outcome is governed by LE CHATELIER’S PRINCIPLE • “...if a system at equilibrium is disturbed, the system tends to shift its equilibrium position to counter the effect of the disturbance.”

  11. Le Chatelier’s Principle • Change in temperature • change in Kc • therefore change in P or concentrations at equilibrium • Use a catalyst: reaction comes more quickly to equilibrium. Kc not changed. • Add or take away reactant or product: • Kc does not change • Reaction adjusts to new equilibrium “position”

  12. 7.2.5 Apply the concepts of kinetics and equilibrium to industrial processes. • A good example of this is the production of ammonia. • Fertilizers and many plastics are derived from ammonia. • High pressure is used to increase yield. • The reaction is exothermic so a lower temperature is used to increase yield. • A catalyst is used to speed up the reaction, but it doesn’t increase the yield.

  13. Haber-Bosch Process for NH3 • N2(g) + 3 H2(g)  2 NH3(g) + heat • K = 3.5 x 108 at 298 K

More Related