Use the observations about each chemical reaction in the table below to decide the sign (positive or entropy A.S. Note: if you have not been given enough information to decide a sign, select the "unknown" option. reaction A B C observations The reaction is never spontaneous. This reaction is exothermic. This reaction is spontaneous only below -9. °C. AH is AS is conclusions AH is AS is AH is AS is (pick one) B (pick one) B (pick one) B (pick one) B (pick one) B (pick one)

Use the observations about each chemical reaction in the table below to decide the sign (positive or entropy A.S. Note: if you have not been given enough information to decide a sign, select the "unknown" option. reaction A B C observations The reaction is never spontaneous. This reaction is exothermic. This reaction is spontaneous only below -9. °C. AH is AS is conclusions AH is AS is AH is AS is (pick one) B (pick one) B (pick one) B (pick one) B (pick one) B (pick one)

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 10.51PAE: 10.51 The combustion of acetylene was used in welder's torches for many years because it produces a...

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On the basis of your experience, predict which of the following reactions are spontaneous. (a) CO2(s)CO2(g) at 25°C (b) NaCl(s)NaCl(l) at 25°C (c) 2NaCl(s)2Na(s)+Cl2(g) (d) CO2(g)C(s)+O2(g)
Calculate S(universe) for the decomposition of 1 mol of liquid water to form gaseous hydrogen and oxygen. Is this reaction spontaneous under standard conditions at 25 C? Explain your answer briefly.
Is the following reaction spontaneous as written? Explain. Do whatever calculation is needed to answer the question. CH4(g)+N2(g)HCN(g)+NH3(g)
For the reaction NO(g)+NO2(g)N2O3(g) , use tabulated thermodynamic data to calculate H and S. Then use those values to answer the following questions. (a) Is this reaction spontaneous at 25°C? Explain your answer. (b) If the reaction is not spontaneous at 25°C, will it become spontaneous at higher temperatures or lower temperatures? (c) To show that your prediction is accurate, choose a temperature that corresponds to your prediction in part (b) and calculate G . (Assume that both enthalpy and entropy are independent of temperature.)
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.
Consider the reaction N2O(g)+NO2(g)3NO(g)K=4.41019 (a) Calculate G for the reaction at 25C. (b) Calculate G f for N2O at 25C.
When ammonium chloride is added to water and stirred, it dissolves spontaneously and the resulting solution feels cold. Without doing any calculations, deduce the signs of G, H, and S for this process, and justify your choices.
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
Predict the sign of S, if possible, for each of the following reactions. If you cannot predict the sign for any reaction, state why. a HCl(g)+NH3(g)NH4Cl(s) b N2(g)+3H2(g)2NH3(g) c 2SO2(g)+O2(g)2SO3(g) d CH3OH(l)+32O2(g)CO2(g)+2H2O(g)
Consider the reaction N2O2(g) 2NO2(g) where PNO2=0.29 atm and PN2O4=1.6. For this reaction at these conditions. G = 1000 J and G = 6000 J. Which of the following statements about this reaction is(are) true? a. The reverse reaction is spontaneous at these conditions. b. At equilibrium. PN2O4 will be greater than 1.6 atm. c. The value of K for this reaction is greater than 1. d. The maximum amount of work this reaction can produce at these conditions is 6000 J. e. The reaction is endothermic.
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.