Practice Problems Exam 3 13 The equilibrium constant for the reaction A B is Kc 10 at a certain temp 1 Starting with only reactant A which of the diagrams shown here best represents the system at equilibrium 2 Which of the diagrams shown here best represents the system at equilibrium if Kc 0 10 Explain why you can calculate Kc in each case without knowing the volume of the container The gray spheres represent the A molecules and the green spheres represent the B molecules 14 The following diagrams represent the equilibrium state for 3 different reactions of the type A X AX X B C or D a Which has the largest equilibrium constant b Which reaction has the smallest equilibrium constant 15 The equilibrium constant Kc for the reaction 2HCl g H2 g Cl2 g Is 4 17 x 10 34 at 25 degrees C What is the equilibrium constant for the reaction H2 g Cl2 g 2HCl g at the same temperature 16 Consider the following equilibrium process at 700 degrees C 2H2 g S2 g 2H2S g Analysis shows that there are 2 50 moles of H2 1 35 x 10 5 moles of S2 an 8 70 moles of H2S present in a 12 0 L flask Calculate the equilibrium constant Kc for the reaction 17 What is Kp at 1273 degrees C for the reaction 2CO g O2 g 2CO2 g If Kc is 2 24 x 10 22 at the same temperature 18 The equilibrium constant Kp for the reaction 2SO3 g 2SO2 g O2 g Is 1 8 x 10 5 at 350 degrees C What is Kc for this reaction 19 Consider the following reaction N2 g O2 g 2NO g If the equilibrium partial pressures of N2 O2 and NO are 0 15 atm 0 33 atm and 0 050 atm at 2200 degrees C what is Kp 21 The equilibrium constant Kc for the reaction I2 g 2I g Is 3 8 x 10 5 at 727 degrees C Calculate Kc and Kp for the equilibrium 2I g I2 g at the same temperature 22 At equilibrium the pressure of the reacting mixture CaCO3 s CaO s CO2 g Is 0 105 atm at 350 degrees C Calculate Kp and Kc for this reaction 23 The equilibrium constant Kp for the reaction PCl5 g PCl3 g Cl2 g Is 1 05 at 250 degrees C The reaction starts with a mixture of PCl5 PCl3 and Cl2 at pressures 0 177 atm 0 223 atm and 0 111 atm at 250 degrees C When the mixture comes to equilibrium at that temperature which pressures have decreased and which will have increased 30 The following equilibrium constants have been determined for oxalic acid at 25 degrees C H2C2O4 aq H aq HC2O4 aq Kc 6 5 x 10 2 HC2O4 aq H aq C2O4 2 aq Kc 6 1 x 10 5 Calculate the equilibrium constant for the following reaction at the same temperature H2C2 4 aq 2H aq C2O4 2 aq 31 The following equilibrium constants were determined at 1123 K C s CO2 g 2CO g Kp 1 3 x 10 14 CO g Cl2 g COCl2 g Kp 6 0 x 10 3 Write the equilibrium constant expression Kp and calculate the equilibrium constant at 1123 K for C s CO2 g 2Cl2 g 2COCl2 g 32 At a certain temperature the following reactions have the constants shown S s O2 g SO2 g Kc 4 2 x 10 52 2S s 3O2 g 2SO3 g Kc 9 8 x 10 128 Calculate the equilibrium constant Kc for the following reaction at that temperature 2SO2 g O2 g 2SO3 g 39 The equilibrium constant Kp for the reaction 2SO2 g O2 g 2SO3 g is 5 60 x 10 4 at 350 degrees C The initial pressures of SO2 and O2 in a mixture are 0 350 atm and 0 762 atm respectively at 350 degrees C When the mixture equilibrates is the total pressure less than or greater than the sum of the initial pressures 1 112 atm 40 For the synthesis of ammonia N2 g 3H2 g 2NH3 g The equilibrium constant Kc at 375 degrees C is 1 2 Starting with H2 0 0 76 M N2 0 0 60 M and NH3 0 0 48 M which gases will have increased in concentration and which will have decreased in concentration when the mixture comes to equilibrium 41 For the reaction H2 g CO2 g H2O g CO g At 700 degrees C Kc 0 534 Calculate the number of moles of H2 that are present at equilibrium if a mixture of 0 300 mole of CO and 0 300 mole of H2O is heated to 700 degrees C in a 10 0 L container 44 The dissociation of molecular iodine into iodine atoms is represented as I2 g 2I g At 1000 K the equilibrium constant Kc for the reaction is 3 80 x 10 5 Suppose you start with 0 0456 mole of I2 in a 2 30 L flask at 1000 K What are the concentrations of the gases at equilibrium 45 The equilibrium constant Kc for the decomposition of phosgene COCl2 is 4 63 x 10 3 at 527 degrees C COCl2 g CO g Cl2 g Calculate the equilibrium partial pressure of all the components starting with pure phosgene at 0 760 atm 46 Consider the following equilibrium process at 686 degrees C CO2 g H2 g CO g H2O g The equilibrium concentrations for the reacting species are CO 0 050 M H2 0 045 M CO2 0 086 M and H2O 0 040 M a Calculate Kc for the reaction at 686 degrees C b if we add CO2 to increase its concentration to 0 50 mol L what will the concentrations of all the gases be when equilibrium is reestablished 47 Consider the heterogeneous equilibrium process C s CO2 g 2CO g At 700 degrees C the total pressure of the system is found to be 4 50 atm If the equilibrium constant Kp is 1 52 calculate the equilibrium partial pressures of Co2 and CO 48 The equilibrium constant Kc for the reaction H2 g CO2 g H2O g CO g Is 4 2 at 1650 degrees C Initially 0 80 mol H2 and 0 80 mol CO2 are injected into a 50 L flask Calculate the concentration of each species at equilibrium 53 Consider the following equilibrium system involving SO2 Cl2 and SO2Cl2 SO2 g Cl2 g SO2Cl2 g Predict how the equilibrium position would change if a Cl2 gas were added to the system b SO2Cl2 were removed from the system c SO2 were removed from the system The temperature remains constant 54 Heating solid sodium bicarbonate in a closed vessel establishes the following equilibrium 2NaHCO3 s Na2CO3 s H2O g CO2 g What would happen to the equilibrium position if a some of the CO2 were removed from the system b some solid NaCO3 were added to the system c some of the solid NaHCO3 were removed from the system The temperature …
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