Chapter 20 Thermodynamics Entropy Free Energy and the Direction of Chemical Reactions Chapter 20 Thermodynamics Entropy Free Energy and the Direction of Chemical Reactions 1 Which of the following is true for pure oxygen gas O2 g at 25 C A H f 0 B H f 0 C G f 0 D G f 0 E S 0 Ans E 2 A certain process has Suniv 0 at 25 C What does one know about the process A It is exothermic B It is endothermic C It is spontaneous at 25 C D It will move rapidly toward equilibrium E None of these choices is correct Ans C 3 Which of the following is necessary for a process to be spontaneous A Hsys 0 B Ssys 0 C Ssurr 0 D Suniv 0 E Gsys 0 Ans D 4 Which of the following results in a decrease in the entropy of the system A O2 g 300 K O2 g 400 K B H2O s 0 C H2O l 0 C C N2 g 25 C N2 aq 25 C D NH3 l 34 5 C NH3 g 34 5 C E 2H2O2 g 2H2O g O2 g Ans C 5 Which of the following should have the greatest molar entropy at 298 K A CH4 g B H2O l C NaCl s D N2O4 g E H2 g Ans D 6 Which of the following is true for a system at equilibrium A S sys S surr B S sys S surr C S sys S surr 0 D S univ 0 E None of these is a sufficient condition Ans B 7 Which of the following is always true for an exothermic process A qsys 0 Ssurr 0 D qsys 0 Ssurr 0 B qsys 0 Ssurr 0 E w 0 C qsys 0 Ssurr 0 Ans B Page 275 2013 by McGraw Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied scanned duplicated forwarded distributed or posted on a website in whole or part Chapter 20 Thermodynamics Entropy Free Energy and the Direction of Chemical Reactions 8 Which of the following is always true for an endothermic process A q sys 0 Ssurr 0 D qsys 0 Ssurr 0 B qsys 0 Ssurr 0 E w 0 C qsys 0 Ssurr 0 Ans A 9 Which of the following values is based on the Third Law of Thermodynamics A H f 0 for Al s at 298 K B G f 0 for H2 g at 298 K C S 51 446 J mol K for Na s at 298 K D q sys 0 for H2O l H2O s at 0 C E None of these choices is correct Ans C 10 When a sky diver free falls through the air the process is A non spontaneous because he is accelerating due to the force applied by gravity B non spontaneous because he is losing potential energy C non spontaneous because he had planned the jump for two weeks D spontaneous E in equilibrium Ans D 11 Which if any of the following processes is spontaneous under the specified conditions A H2O l H2O s at 25 C B CO2 s CO2 g at 0 C C 2H2O g 2H2 g O2 g D C graphite C diamond at 25 C and 1 atm pressure E None of these is spontaneous Ans B 12 Which relationship or statement best describes S for the following reaction Pb s Cl2 g PbCl2 s A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans B Page 276 2013 by McGraw Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied scanned duplicated forwarded distributed or posted on a website in whole or part Chapter 20 Thermodynamics Entropy Free Energy and the Direction of Chemical Reactions 13 Which relationship or statement best describes S for the following reaction HgS s O2 g Hg l SO2 g A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans C 14 Which relationship or statement best describes S for the following reaction 2H2S g 3O2 g 2H2O g 2SO2 g A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans B 15 Which relationship best describes S for the following reaction CO g H2O g CO2 g H2 g A S H B S H T C S 0 D S 0 E S 0 Ans E 16 Which relationship or statement best describes S for the following reaction 2NH3 g 2ClF3 g 6HF g N2 g Cl2 g A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans C 17 Which relationship best describes S for the following reaction 8H2 g S8 s 8H2S g A S H B S H T C S 0 D S 0 E S 0 Ans E 18 Which relationship or statement best describes S for the following reaction O3 g NO g O2 g NO2 g A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans A Page 277 2013 by McGraw Hill Education This is proprietary material solely for authorized instructor use Not authorized for sale or distribution in any manner This document may not be copied scanned duplicated forwarded distributed or posted on a website in whole or part Chapter 20 Thermodynamics Entropy Free Energy and the Direction of Chemical Reactions 19 Which relationship or statement best describes S for the following reaction C2H5OH l 3O2 g 2CO2 g 3H2O l A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans B 20 Which relationship or statement best describes S for the following reaction K2SO4 s 2K aq SO42 aq A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans C 21 Which relationship or statement best describes S for the following reaction BaCl2 aq Na2SO4 aq BaSO4 s 2NaCl aq A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans B 22 Which relationship or statement best describes S for the following reaction CaO s CO2 g CaCO3 s A S 0 B S 0 C S 0 D S H T E More information is needed to make a reasonable prediction Ans B 23 Which of the following pairs has the member with the greater molar entropy listed first All systems are at 25 C A CO g CO2 g D Li s Pb s …