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Changing Concentrations

Changing Concentrations. Changing Rates. R  P Equilibrium lies to right (favors products or forward rxn) R  P Equilibrium lies to left (favors reactants or reverse rxn ). A<---->B k f [A] = k r [B] k f /k r = [B]/[A]

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Changing Concentrations

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  1. Changing Concentrations

  2. Changing Rates

  3. R P • Equilibrium lies to right (favors products or forward rxn) • RP • Equilibrium lies to left (favors reactants or reverse rxn )

  4. A<---->B • kf [A] = kr [B] • kf/kr= [B]/[A] • k(eq) =[B]/[A] • k(eq) = equilibrium constant

  5. aA+ bB <-------> cC + dD • R and P are either g or aq • Equilibrium expression • K (eq) = [C]c[D]d=[products] • [A]a[B]b [reactants] • solids and liquids are not included in expression • If the only product is a solid or liquid- substitute the number 1 for concentration

  6. \ • If K eq > 1000 (103) lot more products • equilibrium lies to the right • if K eq is greater than 105 the reaction essentially goes to completion • The larger the K eq, the more the products are favored • If K eq < 10-3 lot more reactants • equilibrium lies to the left • A very very small Keq indicates that the reaction does not take place. • The smaller the Keq the more the reactants are favored

  7. 2 SO2(g) + O2(g)<----> 2 SO3(g) 3.0 moles of SO2 and 1.5 mole of O2 are placed in a one liter container and react. At equilibrium 1.8 moles of SO3 are present. Determine the equilibrium constant (Keq).

  8. 2NO2 <-------->N2O4

  9. PCl5(g)  PCl3(g) + Cl2(g) • K (eq) = 2.2 x 10-2 If concentrations are: [PCl5 ] = 2.1 x10 -2 [PCl3 ] = 2.0 x10 -1 [Cl2 ] = 2.0 x10 -1 Is the reaction at equilibrium? If not, which way does it need to shift?

  10. Le Chatelier’s Principle • If a reaction at equilibrium is disturbed, the reaction returns to equilibrium by shifting in such a direction as to partially undo (oppose) the disturbance. • New concentrations (equilibrium positions) are established, but the K(eq) remains the same • K(eq) only changes when temperature changes

  11. A(aq) + B(g) <-----> 2C(aq) + D(aq) • If D is added • What will the system want to do with the added D?______ • Which way will the equilibrium shift? ________ • At new equilibrium positions how will concentrations compare to original concentrations? • [A] _________ • [B] _________ • [C] _________ • [D] _________ • What if D was a solid?

  12. A(aq) + B(g) <-----> 2C(aq) + D(aq) • If the pressure is increased (for pressure changes look only at the number of gas molecules on each side of the equation) • What will the system want to do when the pressure is increased? ___________ • Which way will the equilibrium shift? ________ • How could you change the pressure ? ____________

  13. A(aq) + B(g) <-----> 2C(aq) + D(aq) ΔE = -100 kJ • If heat is added • What will the system want to do with the added heat? ________ • Which way will the equilibrium shift? ________ • At new equilibrium positions how will concentrations compare to original concentrations? • [A] _________ • [B] _________ • [C] _________ • [D] _________

  14. A(aq) + B(g) <-----> 2C(aq) + D(aq) ΔE = +100 kJ • If heat is added • What will the system want to do with the added heat? ________ • Which way will the equilibrium shift? ________ • At new equilibrium positions how will concentrations compare to original concentrations? • [A] _________ • [B] _________ • [C] _________ • [D] _________

  15. A(aq) + B(g) <-----> 2C(aq) + D(aq) • If A is added • What will the system want to do with the added A? ________ • Which way will the equilibrium shift? ________ • At new equilibrium positions how will concentrations compare to original concentrations? • [A] _________ • [B] _________ • [C] _________ • [D] _________

  16. SOLUBILITY EQUILIBRIA • When a solution is saturated it is at equilibrium. • equilibrium expressions for ionic solids dissolving in water

  17. PbF2(s) <-->Pb2+(aq) + 2F-(aq) • Keq = equilibrium constant • Ksp = solubility product constant • A small Ksp - reactants favored (not much solid dissolves). • A large Ksp -products favored (solid dissolves.)

  18. From solubility (how much dissolves) can find the solubility product constant. (Ksp) • From the solubility product constant (Ksp) can find the solubility

  19. If the solubility of PbF2 is 1.9 x 10-2 M, what is the solubility product constant (Ksp)? • Write the equation for the reaction. • Write the Ksp expression. • Determine the concentration (M) of each ion. • Solve

  20. If the solubility product constant (Ksp) for BaSO4 is 1.6 x 10 -9,what is the solubility of BaSO4? • Write the equation for the reaction. • Write the Ksp expression. • Let the solubility of BaSO4 equal X. • Solve

  21. Iron(II) hydroxide has a solubility product constant (Ksp) of 1.6 x10 -14 • Write the equation for the dissolving of iron(II) hydroxide. • Write the Ksp expression for the reaction • What is the solubility of iron(II) hydroxide?

  22. What is the concentration of each ion? • How many grams of iron(II) hydroxide can dissolve in 3.5 liters of solution? (total volume)

  23. Calcium phosphate has a solubility product constant of 1.2 x 10 -26. Determine the solubility of calcium phosphate.

  24. Common ion effect and Ksp • Ksp for BaSO4 is 1.6 x 10 -9 • What is the solubility of BaSO4 in a 0.02M Ba(NO3)2 solution?

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