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Chapter18

Chapter18. Reversible reactions Equilibrium Equilibrium expression (K) Equilibrium constant (K). K = [prod] p / [react] r If the value of K is large then products are preferred. If the value of K is small then reactants are preferred. Change in Equilibrium Pressure Concentration

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Chapter18

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  1. Chapter18 • Reversible reactions • Equilibrium • Equilibrium expression (K) • Equilibrium constant (K)

  2. K = [prod]p / [react]r • If the value of K is large then products are preferred. If the value of K is small then reactants are preferred.

  3. Change in Equilibrium • Pressure • Concentration • Temperature • Common Ion

  4. Reactions that form gas • Reactions that form a precipitate

  5. Acid Equilibrium constant Ka • HF + H2O <--> H3O+ + F- • Ka = [H3O+][F-] / [HF] • Base Equilibrium constant Kb • NH3 + H2O <--> OH- + NH4+ • Kb = [OH-][NH4+] / [NH3]

  6. Hydrolysis - the reaction of ions with water • Ions that result in forming a strong acid or base don’t hydrolyze • Cl- + H2O would make HCl which separates back to Cl-

  7. Solubility Equilibrium • Solubility Product constant Ksp • Since the reactant is a solid its not part of the equation • AgI (s) <--> Ag+ + I- • Ksp = [Ag+][I-]

  8. We can use a Ksp value to calculate the solubility of a chemical and the amount of each ion present. • AgBr (s) <--> Ag+ + Br- Ksp = 5 x 10-13 • Ksp = [Ag+][Br-] = 5 x 10-13 • (x)(x) = x2 = 5 x 10-13 • x = 2.24 x 10-6 this is the amount of AgBr that dissolves and also the amount of each ion present

  9. If the calculated solubility product is greater than the actual value then a precipitate will form. • Make sure to use total volume when calculating the concentration of each ion in a solution. • Example on Board

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