Catalyst What parts of the test do you think went better than usual? What parts of the test do you think did not go as well as usual? How are things going for the class? What do you need changed? What do you want kept? (No…homework wil not be reduced and lectures will likely stay as long as they have been )

Cobalt Chloride

Lecture 7.1 – Dynamic Equilibrium and Equilibrium Constants

Today’s Learning Targets LT 7.1 – I can describe the concept of dynamic equilibrium for a given chemical process and incorporate the idea of concentration of products and reactants. LT 7.2 – I can write the equilibrium constant expression, Kc or Kp, for any aqueous or gaseous equilibrium. LT 7.3 – I can calculate the equilibrium constant (Kc or Kp­) from given equilibrium concentrations. LT 7.4 –I can characterize the side of reaction that equilibrium favors using the equilibrium constant.

Equilibrium and Rates ⇌ The equilibrium below is two reactions: N2O 2NO2 There is the forward reaction: The reverse reaction is: At equilibrium the rate of the forward reaction is equal to the reverse reaction: ⇌ Write the rate laws for both the forward and reverse reactions

Dynamic Equilibrium At equilibrium, the rate of the forward and reverse reaction are equal, but continue to occur. We are at dynamic equilibrium because the reaction is occurring, but rates are equal.

Equilibrium Constants (K) The ratio of products to reactants in equilibrium is known as the equilibrium constant (K) Only written for aqueous and gaseous substances. Liquids and gases do not participate in equilibrium. For the general reaction: aA (aq) + bB (aq) cC (aq) + dD (aq) The equilibrium constant (Kc) for all aqueous substances is: ⇌

Gaseous Equilibrium Constants (Kp) When the substances in an equilibrium, we can calculate the equilibrium constant using partial pressures. This is represented as Kp Kp≠Kc For the equilibrium: aA (g) + bB (g) cC (g) + dD (g) ⇌

Class Example Write the equilibrium constant for the following equilibrium: 2 NO (g) + Cl2 (g) 2NOCl (g) ⇌

Ag+ (aq) + 2 NH3 (aq) Ag(NH3)2+ (aq) Table Talk Write the equilibrium constant for the following equilibrium: Ag+ (aq) + 2 NH3 (aq) Ag(NH3)2+ (aq) ⇌

Quick Write Which side of the equilibrium do you think is favored in the reaction below based on the value of Kp. Justify your response. CO (g) + Cl2 (g) COCl2 (g) Kp = 4.56 x 109 ⇌

What K Tells Us A large K indicates that there are more products than reactants at equilibrium A small K indicates that there are more reactants than products at equilibrium If K >> 1, then it is products favored If K << 1, then it is reactants favored

Class Example After mixture of hydrogen and nitrogen gases in a reaction vessel are allowed to attain equilibrium at 472 oC, it is found to contain 7.38 atm H2, 2.46 atm N2, and 0.166 atm NH3. From these data calculate the equilibrium constant, Kp, and state whether it is product or reactants favored: N2 (g) + 3 H2 (g) 2 NH3 (g) ⇌

CH3COOH (aq) H+ (aq) + CH3COO- (aq) Table Talk An aqueous solution of acetic acid is found to have the following equilibrium concentrations at 25 oC: [CH3COOH] = 1.65 x 10-2 M; [H+] = 5.44 x 10-4 M; and [CH3COO-] = 5.44 x 10-4 M. Calculate the equilibrium constant, Kc, for the ionization of acetic acid at 25 oC and state whether it is product or reactant favored: CH3COOH (aq) H+ (aq) + CH3COO- (aq) ⇌

Pass the Paper Please In groups of 3, complete the activity that was passed out. Group member 1 starts on problem 1a, 2 on 2a, and 3 on 3a. Once complete pass the paper to the person next to you and complete problem b for that problem. Do until problems are complete.

Exit Ticket 1. For the chemical reaction: H2 (g) + I2 (g) 2HI (g) Write the equilibrium constant for the reaction. 2. Calculate the equilibrium constant given that once the reaction achieves equilibrium at 25 oC the pressures were measured to be 4.5 atm for H2, 0.132 for I2, and 0.234 atm for HI 3. What side does this equilibrium favor? 4. The following two reactions have equilibrium constants listed: SO2 (g) + ½ O2 (g) SO3 (g) K = 6.2 NO2 (g) NO (g) + ½ O2 K = 14.0 What is the equilibrium constant for the reaction: SO2 (g) + NO2 (g) SO3 + NO (g) ⇌ ⇌ ⇌ ⇌

Closing Time Read: 15.1,15.2, and 15.3 Homework: 15.1, 15.5, 15.15, 15.16, 15.17, 15.19, 15.20, 15.33, and 15.34