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Exam I Thursday, September 28, 7:00-9:00 pm; rooms are on the website. Conflict: (9/28) 4:30-6:30pm in 101 Transportation Building; sign up in 1026 CA Conflict with conflict? Email me right away. Review sessions: Monday (9/25): 165 Noyes Lab; 7-9 pm Tuesday (9/26): 163 Noyes Lab; 7-9 pm

Clicker Question Which of the following is true about chemical or physical equilibrium? a) It is microscopically and macroscopically static. b) It is microscopically and macroscopically dynamic. c) It is microscopically static and macroscopically dynamic. d) It is microscopically dynamic and macroscopically static. e) I do not know.

CO(g) + H2O(g) CO2(g) + H2(g) Clicker Question Consider the following equation: CO(g) + H2O(g) CO2(g) + H2(g) Which of the following must be true at equilibrium? a) [CO2] = [H2] because they are in a 1:1 mole ratio in the balanced equation. b) The total concentration of reactants is equal to the total concentration of the products. c) The total concentration of the reactants is greater than the total concentration of the products. d) The total concentration of the products is greater than the total concentration of the reactants. e) None of these is true.

Change in Concentration/Time

Reaction Rate Over Time

Physical Equilibrium

Change Related to Coefficients

Fe3+(aq) + SCN-(aq) FeSCN2+(aq) Clicker Question You mix 500.0 mL of 4.00 M Fe(NO3)3 with 500.0 mL 6.00 M KSCN. They react according to the following equation:  Fe3+(aq) + SCN-(aq) FeSCN2+(aq)   FeSCN2+ in solution appears red (and the reactants are colorless) so you use a spectrophotometer and determine the concentration of FeSCN2+ at equilibrium to be 1.00 M. Determine the value of the equilibrium constant, K. a) 0.0417 b) 0.0667 c) 0.100 d) 0.167 e) 0.500

Clicker Question Consider the reaction: N2(g) + 3H2(g) 2NH3(g) You initially have 5.0M N2(g) and 12.0M H2(g) and at equilibrium [NH3] = 6.0 M. Determine the value for K at this temperature. a) 0.0083 b) 0.10 c) 0.67 d) 1.0 e) 1.5

K is a Constant (at given T)

Clicker Question For this question, use the balanced equation N2(g) + 3H2(g) 2NH3(g). You have three steel tanks each containing mixtures of N2(g), H2(g), and NH3(g) at the same temperature. The conditions in the tanks are: Tank 1: [N2] = 2.00 M [H2] = 3.00 M [NH3] = 6.00 M Tank 2: [N2] = 2.00 M [H2] = 4.00 M [NH3] = 7.00 M Tank 3: [N2] = 3.00 M [H2] = 2.00 M [NH3] = 4.00 M   Two of the tanks have reach equilibrium. Which tank has not reached equilibrium, and which direction must the reaction proceed in order for that system to reach equilibrium? a) Tank 1 has not reached equilibrium; the reaction in tank 1 must proceed to the left in order to reach equilibrium. b) Tank 1 has not reached equilibrium; the reaction in tank 1 must proceed to the right in order to reach equilibrium. c) Tank 2 has not reached equilibrium; the reaction in tank 2 must proceed to the left in order to reach equilibrium. d) Tank 2 has not reached equilibrium; the reaction in tank 2 must proceed to the right in order to reach equilibrium. e) Tank 3 has not reached equilibrium; the reaction in tank 3 must proceed to the left in order to reach equilibrium.

Clicker Question Dinitrogen pentoxide is added to an evacuated rigid container at 25°C. The initial pressure is 1.000 atm. The N2O5 decomposes according to the equation 2N2O5 (g) 4NO2 (g) + O2(g)   At equilibrium the total pressure is determined to be 1.423 atm. Determine Kp for the reaction. a) 2.77 x 10-2 b) 2.93 x 10-2 c) 7.55 x 10-5 d) 0.111 e) 0.141

NH4OCONH2(s) 2NH3(g) + CO2(g) Clicker Question Ammonium carbamate decomposes as follows:  NH4OCONH2(s) 2NH3(g) + CO2(g) In an experiment carried out in a 10.0-L container at 25°C a certain amount of ammonium carbamate is placed in an evacuated container and allowed to come to equilibrium. When the system has reached equilibrium the total pressure in the flask was observed to be 0.114 atm.   Determine the minimum mass of ammonium carbamate required for the system to reach equilibrium. a) 0.782 g b) 1.22 g c) 2.98 g d) 3.66 g

Heterogeneous Equilibria

Previous Exam Question Gaseous hydrazine (N2H4) decomposes to nitrogen gas and hydrogen gas. At a certain temperature, Kp = 3.50 x 104 for this reaction balanced in standard form. Pure gaseous hydrazine is placed in an otherwise empty rigid vessel and the pressure is noted. The reaction is allowed to reach equilibrium at this temperature and it is observed that the equilibrium pressure is double its initial value. a. Determine the initial pressure of the hydrazine (in atm). Define any variables. b. What percent (in terms of moles) of hydrazine decomposed to reach equilibrium? Explain your answer. c. Determine the equilibrium pressure of hydrazine (in atm).