For a certain chemical reaction, AH" = +9.8 kJ and AS = +30.0 J/K. a) Is the reaction endothermic or exothermie? b) Does the reaction lead to an increase or decrease in the disorder in the system? c) Calculate AG" for the reaction at 100 C. d) No Is the reaction spontaneous at 100 C ? (Cirele one): Yes

For a certain chemical reaction, AH" = +9.8 kJ and AS = +30.0 J/K. a) Is the reaction endothermic or exothermie? b) Does the reaction lead to an increase or decrease in the disorder in the system? c) Calculate AG" for the reaction at 100 C. d) No Is the reaction spontaneous at 100 C ? (Cirele one): Yes

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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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
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.)
Some water is placed in a coffee-cup calorimeter. When 1.0 g of an ionic solid is added, the temperature of the solution increases from 21.5C to 24.2C as the solid dissolves. For the dissolving process, what are the signs for Ssys, Ssurr, and Suniv?
For the reaction at 298 K, 2NO2(g)N2O4(g) the values of H and S are 58.03 kJ and 176.6 J/K, respectively. What is the value of G at 298 K? Assuming that H and S do not depend on temperature, at what temperature is G = 0? Is G negative above or below this temperature?
Given the following information at 25C, calculate G at 25C for the reaction 2A(g)+B(g)3C(g) Substance Hf(kJ/mol) S(J/molK) A(g) 191 244 B(g) 70.8 300 C(g) 197 164 a 956 kJ b 956 kJ c 346 kJ d 346 kJ e 1.03 103 kJ
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.
Use tabulated thermodynamic data to calculate the standard entropy change of each of the reactions listed below. (a) Fe(s)+2HCl(g)FeCl2(s)+H2(g) (b)3NO2(g)+H2O(l)2HNO3(l)+NO(g) (c) 2K(s)+Cl2(g)2KCl(s) (d) Cl2(g)+2NO(g)2NOCl(g) (e) SiCl4(g)Si(s)+2Cl2(g)
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.
10.45 Calculate G at 45°C for reactions for which (a) H = 293 kJ; S= -695 J/K (b) H= -1137 kJ; S = 0.496 kJ/K (c) H = -86.6 kJ; S = -382 J/K
Consider two processes: sublimation of I2(s) and melting of I2(s) (Note: the latter process can occur at the same temperature but somewhat higher pressure). I2(s)I2(g)I2(s)I2(l) Is S positive or negative in these processes? In which of the processes will the magnitude of the entropy change be greater?
Consider two perfectly insulated vessels. Vessel 1 initially contains an ice cube at 0C and water at 0C. Vessel 2 initially contains an ice cube at 0C and a saltwater solution at 0C. Consider the process H2O(s) H2O(l). a. Determine the sign of S, Ssurr, and Suniv for the process in vessel 1. b. Determine the sign of S, Ssurr, and Suniv for the process in vessel 2. (Hint: Think about the effect that a salt has on the freezing point of a solvent.)
Impure nickel, refined by smelting sulfide ores in a blast furnace, can be converted into metal from 99.90% to 99.99% purity by the Mond process. The primary reaction involved in the Mond process is Ni(s)+4CO(g)Ni(CO)4(g) a. Without referring to Appendix 4, predict the sign of S for the above reaction. Explain. b. The spontaneity of the above reaction is temperature-dependent. Predict the sign of Ssurr, for this reaction. Explain c. For Ni(CO)4(g), Hfo=607KJ/mol and S = 417 J/K mol at 298 K. Using these values and data in Appendix 4, calculate H and S for the above reaction. d. Calculate the temperature at which G = 0 (K = 1) for the above reaction, assuming that H and S do not depend on temperature. e. The first step of the Mood process involves equilibrating impure nickel with CO(g) and Ni(CO)4(g) at about 50C. The purpose of this step is to convert as much nickel as possible into the gas phase. Calculate the equilibrium constant for the above reaction at 50.C. f. In the second step of the Mood process, the gaseous Ni(CO)4 is isolated and heated to 227C. The purpose of this step is to deposit as much nickel as possible as pure solid (the reverse of the preceding reaction). Calculate the equilibrium constant for the preceding reaction at 227C. g. Why is temperature increased for the second step of the Mood process? h. The Mond process relies on the volatility of Ni(CO)4 for its success. Only pressures and temperatures at which Ni(CO)4 is a gas are useful. A recently developed variation of the Mood process carries out the first step at higher pressures and a temperature of l52C. Estimate the maximum pressure of Ni(CO)4(g) that can be attained before the gas will liquefy at 152C. The boiling point for Ni(CO)4 is 42C and the enthalpy of vaporization is 29.0 kJ/mol. [Hint: The phase change reaction and the corresponding equilibrium expression are Ni(CO)4(l)Ni(CO)4(g)K=PNi(CO)4 Ni(CO)4(g) will liquefy when the pressure of Ni(CO)4 is greater than the K value.]