Use the observations about each chemical reaction in the table below to decide the sign (positive or negative) of the reaction enthalpy AH and reactionentropy AS.Note: if you have not been given enough information to decide a sign, select the "unknown" option.reactionobservationsconclusionsv (pick one)positivenegativeΔΗ isThis reaction is always spontaneous, butproceeds slower at temperatures below61. °C.AAS isunknownΔΗ is|(pick one) vThis reaction is spontaneous only belowВ20. °C.AS is|(pick one)ΔΗ is|(pick one) ♥CThis reaction is exothermic.AS is|(pick one)B.

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Use the observations about each chemical reaction in the table below to decide the sign (positive or negative) of the reaction enthalpy AH and reaction entropy AS. Note: if you have not been given enough information to decide a sign, select the "unknown" option. reaction observations conclusions AH İs v (pick one) This reaction is always spontaneous, but proceeds slower at temperatures below positive negative A. 61. °C. AS is unknown ΔΗ is |(pick one) ♥ This reaction is spontaneous only below 20. °C. B AS is (pick one) ♥ AH is (pick one) v This reaction is exothermic. AS is |(pick one) v ?

Use the observations about each chemical reaction in the table below to decide the sign (positive or negative) of the reaction enthalpy AH and reaction entropy AS. Note: if you have not been given enough information to decide a sign, select the "unknown" option. reaction observations conclusions AH İs v (pick one) This reaction is always spontaneous, but proceeds slower at temperatures below positive negative A. 61. °C. AS is unknown ΔΗ is |(pick one) ♥ This reaction is spontaneous only below 20. °C. B AS is (pick one) ♥ AH is (pick one) v This reaction is exothermic. AS is |(pick one) v ?

Chemistry for Engineering Students

4th Edition

ISBN:9781337398909

Author:Lawrence S. Brown, Tom Holme

Publisher:Lawrence S. Brown, Tom Holme

Chapter10: Entropy And The Second Law Of Thermodynamics

Section: Chapter Questions

Problem 10.91PAE: The reaction shown below is involved in the refining of iron. (The table that follows provides all...

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Thermite reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite reaction is Fe2O3(s)+2Al(s)Al2O3(s)+2Fe(s). Is the reaction spontaneous at room temperature under standard conditions? During the reaction, the surroundings absorb 851.8 kJ/mol of heat.
The reaction shown below is involved in the refining of iron. (The table that follows provides all of the thermodynamic data you should need for this problem.) 2Fe2O3(s)+3C(s,graphite)4Fe(s)+3CO2(g) (a) Find H for the reaction. (b) S for the reaction above is 557.98 J/K. Find S° for Fe2O3(s). (c) Calculate G for the reaction at the standard temperature of 298 K. (There are two ways that you could do this.) (d) At what temperatures would this reaction be spontaneous? Compound Hf (kJ mol-1) S° (kJ mol-1) Gf (J mol-1 K-1) Fe2O3(s) -824.2 ? -742.2 C(s, graphite) 0 5.740 0 Fe(s) 0 27.3 0 CO2(g) -393.5 213.6 -394.4.83
9.54 The phase change between graphite and diamond is difficult to observe directly. Both substances can be hurned, however. From these equations, calculate H for the conversion of diamond into graphite. C(s,graphite)+O2(g)CO2(g) H= -393.51 kJ C(s,diamond)+O2(g)CO2(g) H= -395.94 kJ
Methane can be produced from CO and H2.The process might be done in two steps, as shown below, with each step carried out in a separate reaction vessel within the production plant. Reaction 1 CO(g)+2H2(g)CH3OH(l) S = -532 J/K Reaction 2 CH3OH(l)CH4(g)+12O2(g) S= +162 J/K NOTE: You should be able to work this problem without using any additional tabulated data. (a) Calculate H for reaction 1. (b) Calculate Gf for CO(g). (c) Calculate S° for O2(g). (d) At what temperatures is reaction 1 spontaneous? (e) Suggest a reason why these two steps would need to be carried out separately. Substance Hf (kJ mol-1) Gf (kJ mol-1) S (J mol-1 K-1) CO(s) -110.5 197.674 CH3OH( l ) -238.7 -166.4 126.8 CH4(g) -74.8 186.2
10.51 The combustion of acetylene was used in welder's torches for many years because it produces a very hot flame: C2H2(g)+52O2(g)2CO2(g)+H2O(g) H= -1255.5 kJ (a) Use data in Appendix E to calculate S for this reaction, (b) Calculate G and show that the reaction is spontaneous at 25°C. (c) Ls there any temperature range in which this reaction is not spontaneous? (d) Do you think you could use Equation 10.4 to calculate such a temperature range reliably? Explain your answer.
For the reaction C2H2(g)+4F2(g)2CF4(g)+H2(g) S is equal to 358 J/K. Use this value and data from Appendix 4 to calculate the value of S for CF4(g).
Define the standard enthalpy of formation. What are standard states for elements and for compounds? Using Hess's law, illustrate why the formula Hreaction=npHf(products)nfHf(reactants) works to calculate H for a reaction.
Nickel metal reacts with carbon monoxide to form tetra-carbonyl nickel, Ni(CO)4: Ni(s)+4CO(g)Ni(CO)4(g) This reaction is exploited in the Mond process in order to separate pure nickel from other metals. The reaction above separates nickel from impurities by dissolving it into the gas phase. Conditions are then changed so that the reaction runs in the opposite direction to recover the purified metal. (a) Predict the sign of S for the reaction as written above. (b) Use tabulated thermodynamic data to calculate H, S , and G for the reaction. (c) Find the range of temperatures at which this reaction is spontaneous in the forward direction.
Recall that incomplete combustion of fossil fuels occurs when too little oxygen is present and results in the production of carbon monoxide rather than carbon dioxide. Water is the other product in each case. (a) Write balanced chemical equations for the complete and incomplete combustion of propane. (b) Using these equations, predict which will have the larger change in entropy. (c) Use tabulated thermodynamic data to calculate G for each reaction. (d) Based on these results, predict the sign and value of G for the combustion of carbon monoxide to form carbon dioxide.