Exam 1 Chapter 15 17 4 Chemical and Solubility Equilibria Chem 1202 Form 2 Fall 2024 Dr Gasery Answer Key Instructions Use an 8 5 x 11 inch green and white scantron On Side Two of the scantron 1 Print your Last Name then First Name and bubble it in 2 Print and bubble in your complete correct LSU ID number 89 number 3 Bubble 2 in the Grade or Education box On Side One of the scantron sheet using a pencil blank 1 Print your name 2 Answers to the exam questions must go on side one Bubble the answers on the scantron 3 There is exactly one best answer for each question and you should NOT leave a question 4 On a numerical question choose the response closest to the correct answer This exam is closed notes and closed book You are not allowed to use your own scratch paper Only a scientific calculator is allowed during the exam NO graphing calculators Mark your answers in your Exam for future reference You can keep your Exam for further study Present your LSU ID and the front of your exam when submitting your scantron Useful Information and Constants The periodic table is located at the back of the exam R 0 08206 L atm mol K Kp Kc RT n 1 a NO2 N2O4 b NO2 2 N2O4 c NO2 N2O4 2 d NO2 N2O4 e NO2 2 N2O4 a K2 b 2K c 1 2K d 1 K2 e K2 a 13 3 b 3 65 c 0 0376 d 5 66 x 10 3 e 26 6 1 Which of the following statements concerning a reaction at equilibrium is TRUE a All chemical reactions have ceased b The rates of the forward and reverse reactions are equal c The rate constants of the forward and reverse reactions are equal d The value of the equilibrium constant is 1 e The limiting reagent has been consumed 2 Which one of the following will change the value of the equilibrium constant Kc a Changing the temperature b Adding other substances that do not react with any of the species involved in the equilibrium c Varying the initial concentrations of reactants d Varying the initial concentrations of products e Changing the volume of the reaction vessel 3 Choose the correct equilibrium expression for the reaction below N2O4 g 2NO2 g 4 Review the two chemical reactions below If the equilibrium constant for Reaction I is K which would be the correct equilibrium constant for Reaction II I II SO2 g 1 2O2 g 2SO3 g SO3 g 2SO2 g O2 g 5 The Keq for the following equilibrium is 7 52 x 10 2 at 480 C 2Cl2 g 2H2O g 4HCl g O2 g What is the value of Keq at this temperature for the reaction below 2HCl g 1 2O2 g Cl2 g H2O g The difference between the first reaction and the second reaction is that the first reaction has been reversed and multiplied by Keq for Reaction 2 1 K 1 7 52 x 10 2 1 2 3 65 2 6 Consider the following reaction at equilibrium H2 g Br2 g 2HBr g if the value of Kc is 1 9 x 1019 at 25 C calculate the value of Kp for the reaction at this temperature a 5 26 x 10 19 b 1 56 x 104 c 6 44 x 105 d 1 90 x 1019 e None of the above 7 Choose the correct equilibrium expression for the reaction below NH4 2Se s 2NH3 g H2Se g a NH3 H2Se NH4 2Se b NH4 2Se NH3 2 H2Se c 1 NH4 2Se d NH3 2 H2Se e NH3 2 H2Se NH4 2Se 8 At 400 K the equilibrium constant for the reaction Br2 g Cl2 g 2BrCl g is Kp 7 0 A closed vessel at 400 K is charged with 1 00 atm of Br2 g 1 00 atm of Cl2 g and 2 00 atm of BrCl g Use Q to determine which of the statements below is TRUE a The equilibrium partial pressures of Br2 Cl2 and BrCl will be the same as the initial b The equilibrium partial pressure of BrCl g will be 4 00 atm c The equilibrium partial pressure of Br2 will be greater than 1 00 atm d At equilibrium the total pressure in the vessel will be less than the initial total values pressure e The reaction will go to completion since there are equal amounts of Br2 and Cl2 This question Question 8 did not give a fair answer choice If marked wrong on the score report you received credit back In other words everyone received credit for this question whether it was marked wrong or not 9 Consider the following reaction at equilibrium 2NH3 g N2 g 3H2 g LeChatelier s principle predicts that the moles of H2 in the reaction container will increase with a some removal of NH3 from the reaction vessel V and T constant b a decrease in the total pressure T constant c addition of some N2 to the reaction vessel V and T constant d a decrease in the total volume of the reaction vessel T constant e an increase in total pressure by the addition of helium gas V and T constant 10 What is the effect of a catalyst on a system at equilibrium a increase the rate of the forward reaction only b increase the equilibrium constant so that products are favored c slow the reverse reaction only 3 d increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture e shift the equilibrium to the right 11 Consider the following chemical reaction CO g 2H2 g CH3OH g At equilibrium the concentrations of CO and H2 were 0 15 M and 0 36 M respectively What is the equilibrium concentration of CH3OH The value of Keq for this reaction is 14 5 at the temperature of this experiment a 14 5 b 7 61 x 10 3 c 2 82 x 10 1 d 3 72 x 10 3 e 1 34 x 10 3 12 Dinitrogen tetraoxide partially decomposes into nitrogen dioxide according to the 2NO2 g A 1 00 L flask is charged with 0 0400 following equilibrium N2O4 g mol of N2O4 At equilibrium at 373 K 0 0055 mol of N2O4 remains Calculate Keq for this reaction a 2 2 x 10 4 b 13 c 0 22 d 0 87 e 0 022 Use the following table of Ksp values to answer Questions 13 and 14 13 Which compound listed in the table has the greatest molar solubility in water 14 Which compound listed in the table has the smallest molar solubility in water a CdCO3 b Cd OH 2 c CaF2 d AgI e ZnCO3 a CdCO3 b Cd OH 2 c CaF2 d AgI 4 15 What is the concentration of iodide ions in a saturated solution of lead II iodide The solubility product constant Ksp of PbI2 is 1 4 x 10 8 a 3 8 10 …