Choose the word from the word bank below that best matches each statement. Constant Equilibrium Increases Temperature Chemical Endothermic Reactant Closed system Exothermic Reversible 1. When the rate of the forward reaction is equal to the rate of backward reaction, the system is said to be in 2. Equilibrium can only be established when all particles are kept in a sealed container and certain conditions are kept. 3. In a reversible reaction, when the rate at which products are formed equals the rate at which reactants are formed, we say that the reaction has reached equilibrium. a 4. Equilibrium constants are specific for only one reaction at a particular 5. If the forward reaction is endothermic, increasing the temperature the value of the equilibrium constant.

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

. 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 inter-conversion reaction?

. Ammonia. a very important industrial chemical. is produced by the direct combination of the following elements under carefully controlled conditions: N2(g)+3H2(g)2NH3(g)Suppose. in an experiment, that the reaction mixture is analyzed after equilibrium is reached, and it is found, at a particular temperature. that [NH3]=0.25M,[H2]=3.4103M, and [N2]=5.3105M. Calculate the value of K at this temperature.

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?

The following series of diagrams represent the reaction XY followed over a period of time. The X molecules are red and the Y molecules are green. At the end of the time period depicted, has the reaction system reached equilibrium? Justify your answer with a one-sentence explanation.

Chemical Equilibrium II Magnesium hydroxide. Mg(OH)2, is a white, partially soluble solid that is used in many antacids. The chemical equation for the dissolving of Mg(OH)2(s) in water is Mg(OH)2(s)Mg2+(aq)+2OH(aq) a Describe a simple experimental procedure that you could use to study this solubility equilibrium. In your experiment, how would you determine when the solution process has attained equilibrium? b Write the equilibrium-constant expression for this dissolving of magnesium hydroxide. c Suppose equilibrium has been established in a container of magnesium hydroxide in water, and you decide to add more solid Mg(OH)2. What would you expect to observe? What effect will this addition of Mg(OH)2 have on the concentrations of Mg2+(aq) and OH(aq)? d Say you haw prepared an equilibrium solution of Mg(OH)2 by adding pure solid Mg(OH)2 to water. If you know the concentration of OH(aq), can you determine the concentration of Mg2+(aq)? If not, what information do you need that will allow you to determine the answer? e You slowly add OH from another source (say, NaOH) to an equilibrium mixture of Mg(OH)2 and water. How do you expect the concentration of the Mg2+(aq) to change? What might you be able to observe happening to the Mg(OH)2(s) as you add the OH? f Next you remove some, but not all, of the Mg(OH)2(s) from the mixture. How will this affect the concentrations of the Mg2+(aq) and OH(aq)? g If someone hands you a container of Mg(OH)2(aq) and there is no solid Mg(OH)2 present, is this solution at equilibrium? If it is not at equilibrium, what could you add to or remove from the container that would give an equilibrium system? h Consider an individual OH(aq) ion in an Mg(OH)2 solution at equilibrium. If you could follow this ion over a long period of time, would you expect it always to remain as an OH(aq) ion, or could it change in some way?

. Explain why the development of a vapor pressure above a liquid in a closed container represents an equilibrium. What are the opposing processes? How do we recognize when the system has reached a state of equilibrium?

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?

Describe a nonchemical system that is in equilibrium, and explain how the principles of equilibrium apply to the system.