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Chemistry 1011

Chemistry 1011. TOPIC Gaseous Chemical Equilibrium TEXT REFERENCE Masterton and Hurley Chapter 12. 12.3 Determination of K. YOU ARE EXPECTED TO BE ABLE TO: Calculate the value of K from experimental data for the system at equilibrium

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Chemistry 1011

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  1. Chemistry 1011 TOPIC Gaseous Chemical Equilibrium TEXT REFERENCE Masterton and Hurley Chapter 12 Chemistry 1011 Slot 5

  2. 12.3 Determination of K YOU ARE EXPECTED TO BE ABLE TO: • Calculate the value of K from experimental data for the system at equilibrium • Calculate the value of K from experimental data for the system at the start of a reaction and at equilibrium Chemistry 1011 Slot 5

  3. Determination of K from Equilibrium Data • Write a balanced equation for the equilibrium • Write an expression for the equilibrium constant • Input equilibrium partial pressures of components • Calculate K Chemistry 1011 Slot 5

  4. Determination of K from Equilibrium Data • Ammonium chloride decomposes on heating • At 400oC, 12.0g of NH4Cl is present in a closed system. The partial pressures of NH3 and HCl are 3.0atm and 5.0atm. • Calculate K NH4Cl(s) NH3(g) + HCl(g) KP = PNH3 x PHCl = 3.0 x 5.0 = 15 Chemistry 1011 Slot 5

  5. Determination of K from Initial and Equilibrium Data • Write a balanced equation for the equilibrium • Write an expression for the equilibrium constant • Distinguish equilibrium from initial partial pressures • Use stoichiometry to determine equilibrium partial pressures from initial partial pressure data • Input equilibrium partial pressures of components • Calculate K Chemistry 1011 Slot 5

  6. Determination of K from Initial and Equilibrium Data • Consider the system: 2HI(g) H2(g) + I2(g) • Initially, a system contains HI only, at a pressure of 1.00atm at 520oC. • At equilibrium, the partial pressure of H2(g) is found to be 0.10atm • Find • PI2 at equilibrium • PHI at equilibrium • Kp Chemistry 1011 Slot 5

  7. Determination of K from Initial and Equilibrium Data 2HI(g) H2(g) + I2(g) Initially 1.00atm 0.00atm 0.00atm At equilibrium ? 0.10atm ? 2 moles of HI must react in order to produce 1 mole of H2 At the same time, 1 mole of I2 will be produced Partial pressure is proportional to the number of moles of gas DP -0.20atm +0.10atm +0.10atm At equilibrium 0.80atm 0.10atm 0.10atm Kp =PH2 xPI2 = 0.10 x 0.10 =0.016 (PHI )2 (0.80)2 Chemistry 1011 Slot 5

  8. Equilibrium Reaction of NOBr • 2.00atm of NOBr(g) are placed into a closed container at 350oC • NOBr(g) decomposes to NO(g) and Br2(g) and an equilibrium is established • At equilibrium, the partial pressure of Br2 is 0.25atm • Write an equation for the equilibrium • Write an expression for Kp • Evaluate Kp for the reaction at 350oC Chemistry 1011 Slot 5

  9. Equilibrium Reaction of NOBr 2 NOBr(g) 2NO(g) + Br2(g) Initial 2.00atm 0.00atm 0.00atm Equilibrium ? ? 0.25atm Each mole of NOBr that decomposes will produce 1 mole of NO and ½ mole of Br2 DP -0.50atm +0.50atm +0.25atm Equilibrium 1.50atm 0.50atm 0.25atm Kp = (PNO)2 x PBr2 = (0.50)2 x (0.25) = 2.8 x 10-2 (PNOBr)2 (1.50)2 Chemistry 1011 Slot 5

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