1. In your own words, explain the difference between the equilibrium constant, K, and the reaction quotient, Q. How do we use K and Q to determine what will happen to a specific reaction under a given set of conditions?

1. In your own words, explain the difference between the equilibrium constant, K, and the reaction quotient, Q. How do we use K and Q to determine what will happen to a specific reaction under a given set of conditions?

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter14: Chemical Equilibrium

Section: Chapter Questions

Problem 77AP

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Kc = 5.6 1012 at 500 K for the dissociation of iodine molecules to iodine atoms. I2(g) 2 I(g) A mixture has [I2] = 0.020 mol/Land [I] = 2.0 108 mol/L. Is the reaction at equilibrium (at 500 K)? If not, which way must the reaction proceed to reach equilibrium?
The initial concentrations or pressures of reactants and products are given for each of the following systems. Calculate the reaction quotient and determine the direction in which each system will proceed to reach equilibrium. (a) 2NH3(g)N2(g)+3H2(g) Kc=17;[NH3]=0.50M,[N2]=0.15M,[H2]=0.12M (b) 2NH3(g)N2(g)+3H2(g) Kp=6.8104 initial pressures NH3=2.00atm,N2=10.00atm,H2=10.00atm (c) 2SO3(g)2SO2(g)+O2(g) Kc=0.230;[SO3]=2.00M,[SO2]=2.00M,[O2]=2.00M (d) 2SO3(g)2SO2(g)+O2(g) Kp=16.5 initial pressures SO2=1.00atm,O2=1.130atm,SO3=0atm (e) 2NO(g)+CI2(g)2NOCI(g) Kp=2.5103 ; initial pressures; NO=1.00atm,CI2=1.00atm,NOCI=0atm (f) N2(g)+O2(g)2NO(g) Kc=0.050 ; [N2]=1.00M,[O2]=0.200M,[NO]=1.00M
Write the mathematical expression for the reaction quotient, QC, for each of the following reactions (a) N2(g)+3H2(g)2NH3(g) (b) 4NH3(g)+5O2(g)4NO(g)+6H2O(g) (C) N2O2(g)2NO2(g) (d) CO2(g)+H2CO(g)+H2O(g) (e) NH4CI(s)NH3(g)+HCI(g) (f) 2Pb( NO3)2(s)2PbO(s)+4NO2(g)+O2(g) (g) 2H2(g)+O2(g)2H2O(g) (h) S8(g)8S(g)
Many sugars undergo a process called mutarotation, in which the sugar molecules interconvert between two isomeric forms, finally reaching an equilibrium between them. This is true for the simple sugar glucose, C6H12O6, which exists in solution in isomeric forms called alpha-glucose and beta-glucose. If a solution of glucose at a certain temperature is analyzed, and it is found that the concentration of alpha-glucose is twice the concentration of beta-glucose, what is the value of K for the interconversion reaction?
Because carbonic acid undergoes a second ionization, the student in Exercise 12.39 is concerned that the hydrogen ion concentration she calculated is not correct. She looks up the equilibrium constant for the reaction HCO,-(aq) «=* H+(aq) + COf'(aq) Upon finding that the equilibrium constant for this reaction is 4.8 X 10“H, she decides that her answer in Exercise 12.39 is correct. Explain her reasoning. A student is simulating the carbonic acid—hydrogen carbonate equilibrium in a lake: H,CO,(aq) 5=6 H+(aq) + HCO,'(aq) K = 4.4 X 10'7She starts with 0.1000 A1 carbonic acid. W hat are the concentrations of all species at equilibrium?
An experimenter places the following concentrations of gases in a closed container: [NOBr] = 7.13 102 M, [NO] = 1.58 102 M. [Br2] = 1.29 102 M. These gases then react: 2NOBr(g)2NO(g)+Br2(g) At the temperature of the reaction, the equilibrium constant Kc is 3.07 104. Calculate the reaction quotient, Qc, from the initial concentrations and determine whether the concentration of NOBr increases or decreases as the reaction approaches equilibrium. a Qc = 6.33 104; the concentration of NOBr decreases b Qc = 6.33 104; the concentration of NOBr increases c Qc = 1.58 104; the concentration of NOBr increases d Qc = 4.65 104; the concentration of NOBr decreases e Qc = 4.65 104; the concentration of NOBr increases
Chemical Equilibrium I Part 1: You run the chemical reaction C(aq)+D(aq)2E(aq) at 25C. The equilibrium constant Kc for the reaction at this temperature is 2.0. a Write the equilibrium-constant expression for the reaction. b Can you come up with some possible concentrations of C, D, and E that you might observe when the reaction has reached equilibrium at 25C? What are these values? c A student says that only a very limited number of concentrations for C, D, and E are possible at equilibrium. Is this true? State why you think this is true or is not true. d If you start with 1.0 M concentrations of both C and D and allow the reaction to come to equilibrium, would you expect the concentration of C to have decreased to zero? If not, what would you expect for the concentration of C? (An approximate value is fine.) Part 2: Consider the reaction A(aq)F(aq)+G(aq), whose equilibrium constant is 1.0 105 at 20C. For each of the situations described below, indicate whether any reaction occurs. If reaction does occur, then indicate the direction of that reaction and describe how the concentrations of A, B, F, and G change during this reaction. a A(aq) and B(aq) are mixed together in a container. b F(aq) and G(aq) are mixed together in a container. c A(aq) and F(aq) are mixed together in a container. d B(aq) and G(aq) are mixed together in a container. e Just B(aq) is placed into a container. f Just G(aq) is placed into a container. Consider any one of these situations in which a reaction does occur. At equilibrium, does the reaction mixture have appreciably more products than reactants? If not, how would you describe the equilibrium composition of the reaction mixture? How did you arrive at this answer?
For a typical equilibrium problem, the value of K and the initial reaction conditions are given for a specific reaction, and you are asked to calculate the equilibrium concentrations. Many of these calculations involve solving a quadratic or cubic equation. What can you do to avoid solving a quadratic or cubic equation and still come up with reasonable equilibrium concentrations?
At 2300 K the equilibrium constant for the formation of NO(g) is 1.7 103. N2(g) + O2(g) 2 NO(g) (a) Analysis shows that the concentrations of N2 and O2 are both 0.25 M, and that of NO is 0.0042 M under certain conditions. Is the system at equilibrium? (b) If the system is not at equilibrium, in which direction does the reaction proceed? (c) When the system is at equilibrium, what are the equilibrium concentrations?
Is a system at equilibrium if the rate constants of the forward and reverse reactions are equal?
The equilibrium constant for the butane iso-butane equilibrium at 25 C is 2.50. Calculate rG at this temperature in units of kJ/mol.
For the reaction N2(g)+3H2(g)2NH3(g) show that Kc = Kp(RT)2 Do not use the formula Kp = Kc(RT)5n given in the text. Start from the fact that Pi = [i]RT, where Pi is the partial pressure of substance i and [i] is its molar concentration. Substitute into Kc.