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More Equilibrium

More Equilibrium. Objective/Warm-Up. SWBAT use the reaction quotient (Q) in order to determine how a reaction will shift in order to reach equilibrium. 2SO 2 (g) + O 2 (g) 2SO 3 (g)

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More Equilibrium

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  1. More Equilibrium

  2. Objective/Warm-Up • SWBAT use the reaction quotient (Q) in order to determine how a reaction will shift in order to reach equilibrium. • 2SO2(g) + O2(g) 2SO3(g) • In a certain experiment 2.00 mol of SO2, 1.50 mol of O2 and 3.00 mol of SO3 were placed in a 1.00 L flask. At equilibrium 3.50 mol SO3 were found to be present. Calculate • The equilibrium concentrations of O2 and SO2, K

  3. Playing with K • If we write the reaction in reverse. • lC + mD jA + kB • Then the new equilibrium constant is • K’ = [A]j[B]k = 1/K[C]l[D]m

  4. Playing with K • If we multiply the equation by a constant • njA + nkB nlC + nmD • Then the equilibrium constant is • K’ = [A]nj[B]nk= ([A] j[B]k)n= Kn[C]nl[D]nm ([C]l[D]m)n

  5. K is CONSTANT • At any temperature. • Temperature affects rate. • The equilibrium concentrations don’t have to be the same only K. • Equilibrium position is a set of concentrations at equilibrium. • There are an unlimited number.

  6. Equilibrium and Pressure • Some reactions are gaseous • PV = nRT • P = (n/V)RT • P = CRT • C is a concentration in moles/Liter • C = P/RT

  7. Equilibrium and Pressure • 2SO2(g) + O2(g) 2SO3(g) • Kp = (PSO3)2 (PSO2)2 (PO2) • K = [SO3]2 [SO2]2 [O2]

  8. Equilibrium and Pressure • K =(PSO3/RT)2 (PSO2/RT)2(PO2/RT) • K =(PSO3)2 (1/RT)2 (PSO2)2(PO2) (1/RT)3 • K = Kp (1/RT)2= Kp RT (1/RT)3

  9. Kp =K (RT)(l+m)-(j+k) = K (RT)Dn Dn=(l+m)-(j+k)=Change in moles of gas

  10. What Q tells us • If Q<K • Not enough products • Shift to right • If Q>K • Too many products • Shift to left • If Q=K system is at equilibrium

  11. Example • for the reaction • 2NOCl(g) 2NO(g) + Cl2(g) • K = 1.55 x 10-5 M at 35ºC • In an experiment 0.10 mol NOCl, 0.0010 mol NO(g) and 0.00010 mol Cl2 are mixed in 2.0 L flask. • Which direction will the reaction proceed to reach equilibrium?

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