Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.2 Reaction Quotient and Equilibrium Constant 2.2.2 Variations in the Form of Q Summary Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.3 EXPRESSING EQUILIBRIA WITH PRESSURE TERMS: RELATION BETWEEN Kc AND Kp Concentration = number of moles per volume R = 0.0821 atm/mol.K Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.3 EXPRESSING EQUILIBRIA WITH PRESSURE TERMS: RELATION BETWEEN Kc AND Kp If, Then Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.3 EXPRESSING EQUILIBRIA WITH PRESSURE TERMS: RELATION BETWEEN Kc AND Kp Problem Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.3 EXPRESSING EQUILIBRIA WITH PRESSURE TERMS: RELATION BETWEEN Kc AND Kp Problem If the Kc for this chemical equation is 0.500 at a temperature of 300 ºC, then what is the Kp? 2 OF2(g) + 2 NH3(g) <—> N2F4(g) + O2(g) + 3 H2(g) ∆n =1 Kp = 0.5x0.0821x573.15 = 23.53 Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.3 EXPRESSING EQUILIBRIA WITH PRESSURE TERMS: RELATION BETWEEN Kc AND Kp Problem If the Kp for this chemical equation is 8.70 * 10-3 at a temperature of 280.K, then what is the Kc? 2 C4H10(L) + 13 O2(g) <—-> 8 CO2(g) + 10 H2O(g) ∆n =3 Kc = (8.70 * 10-3 )/(0.0821x280)3 = 7.16 * 10-7 Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.4 Reaction Direction and Reaction Quotient, Q Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.4 Reaction Direction and Reaction Quotient, Q products Reactants Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.4 Reaction Direction and Reaction Quotient, Q Qp = (0.24*0.47)/(0.13*0.035) =24.7 Kp is greater than Qp then CH3Cl is formed Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5 HOW TO SOLVE EQUILIBRIUM PROBLEMS 2.5.1 Using quantities to find Kc or Kp 2.5.2 Using Kc to find quantities 2.5.3 detect direction of reaction Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5 HOW TO SOLVE EQUILIBRIUM PROBLEMS 2.5.1 Using quantities to find Kc or Kp) Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.2 Reaction Quotient and Equilibrium Constant 2.5.1 Using quantities to find Kc or Kp) Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.2 Reaction Quotient and Equilibrium Constant 2.5.2 Using Kc to find quantities Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.2 Reaction Quotient and Equilibrium Constant 2.5.2 Using Kc to find quantities Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.2 Reaction Quotient and Equilibrium Constant 2.5.2 Using Kc to find quantities Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5 HOW TO SOLVE EQUILIBRIUM PROBLEMS 2.5.3 detect direction of reaction Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5 HOW TO SOLVE EQUILIBRIUM PROBLEMS 2.5.3 detect direction of reaction Problem Equal amounts of gaseous hydrogen and iodine are injected into a 1.50-L reaction flask at a fixed temperature At equilibrium, analysis shows that the flask contains 1.80 mol of H2, 1.80 mol of I2, and 0.520 mol of HI. convert the amounts (mol) to concentrations (mol/L) [I2] = 1.20 M, and [HI]= 0.347 M Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5 HOW TO SOLVE EQUILIBRIUM PROBLEMS 2.5.3 detect direction of reaction Problem Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle The most remarkable feature of a system at equilibrium is its ability to return to equilibrium after a change in conditions moves it away from that state. Keep Q=K Henry Louis Le Chatelier 1850-1936 French Chemist Disturbance may be: 1- Concentration change. 2- Pressure Change. 3- Temperature Change. Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle Le Châtelier’s principle allows us to predict the direction of the shift in equilibrium position. Most importantly, it helps research and industrial chemists create conditions that maximize yields. • The Effect of a Change in Concentration What does happen to that system at equilibrium if we: • add more Cl2? • add more PCl3? • add more PCl5? Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in Concentration Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in Concentration Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in Concentration adding a solid has no effect on the concentrations of other components: because the concentration of the solid cannot change, it does not appear in Q. Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in pressure(volume) Changes in pressure have significant effects only on equilibrium systems with gaseous components. (liquids and solids they are nearly incompressible) What does happen to the following systems by increasing pressure? shifting the reaction toward the side with fewer moles of gas Keep Q=K Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in pressure(volume) Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in Temperature If we consider heat as a component of the equilibrium system, a rise in temperature occurs when heat is “added” to the system and a drop in Temperature alter K temperature occurs when heat is “removed” from the system. What does happen to the following system by increasing Temperature? Chapter (2): Chemical Equilibrium- The Extent of Chemical Reactions 2.5.3 detect direction of reaction 2.5.3.1 Reaction Conditions and the Equilibrium State Le Châtelier’s Principle • The Effect of a Change in Temperature Temperature alter K
