The Meaning of K K gt 1 the equilibrium position is far to the right K lt 1 the equilibrium position is far to the left The value of K for a system can be calculated from a known set of equilibrium concentrations ID: 1028437
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1. Shifting Equilibrium
2. Applications Involving the Equilibrium ConstantThe Meaning of K K > 1 the equilibrium position is far to the right K < 1 the equilibrium position is far to the left
3. The value of K for a system can be calculated from a known set of equilibrium concentrations. Unknown equilibrium concentrations can be calculated if the value of K and the remaining equilibrium concentrations are known.
4. Le Chatelier’s PrincipleA reaction at equilibrium will proceed in a direction that relieves the stress put on it.The equilibrium position changes, but the equilibrium constant (K) does not change unless temperature changes
5. Factors that “stress” or shift the EquilibriumTemperature - ↑ temp = ↑ reaction rateOnly thing that changes K because it affects the free energy of the reaction!If exothermic, a temperature ↑ will make rxn proceed to the left (to reactants)If endothermic, a temperature ↑ will make rxn proceed to the right (to products)
6. VolumeLook at the number of moles of gas↓ the volume ↑ the pressure, & will cause the reaction to proceed towards the side with fewer moles of gas↓ volume ↑ reaction rate for both the forward & reverse reactions.The side with more moles of gas has an advantage since there are more collision per unit of timeChanging volume does not change K
7. PressureLook at the number of moles of gasPressure can be changed 2 waysChanging volume (see previous slide); changing pressure this was does change reaction rateAdding an inert gas; changing pressure this was does NOT change reaction rateChanging pressure does not change K
8. ConcentrationLook at the reactants & productsIf reactant’s concentration ↑, reaction shifts towards productsIf product’s concentration ↑, reaction shifts towards reactants
9. Can change concentration by:Adding reactant or productRemoving reactant or productAdding something that complete (or almost completely) reacts with the reactant or productsIf you add something that forms a precipitate with one the reactants or products, you are effectively removing that reactant or product
10. Example: 2H2(g) + O2(g) + energy ↔ 2H2O(g)If [H2] increases, reaction will shift to the because more product will be made to use up the excess H2If [H2] decreases, reaction will shift to the to make up some of the H2 that was lost
11. Example: 2H2(g) + O2(g) + energy ↔ 2H2O(g)Is this reaction endothermic or exothermic? If temp. increases, reaction will shift to the energy is a reactant, will shift right to use up the added energyIf temp. decreases, reaction will shift to the energy is a reactant, will shift left to make up the energy that is being lostWhen pressure ↑, & volume ↓, reaction shifts to make fewer moles of gasWhen pressure ↓, & volume ↑, reaction shifts to make more moles of gas