Calculate the ?G° from the standard enthalpy of formation and standard molar entropy values, and predict whether the reaction is spontaneous or not at 25 ℃.   Fe2O3 (s)   +   3H2 (g)   →   2Fe (s)   +   3H2O (g)   ?H° (kJ / mol) ?S° (J / mol.K) Fe2O3 (s) 822.2 90.0 H2 (g) 0 130.6  Fe (s) 0 27.2  H2O (g) 241.8  188.8

Solid NH4NO3 is placed in a beaker containing water at 25 C. When the solid has completely dissolved, the temperature of the solution is 23.5 C. (a) Was the process exothermic or endothermic? (b) Was the process spontaneous? (c) Did the entropy of the system increase? (d) Did the entropy of the universe increase?

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.)

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.

How does the second law of thermodynamics explain a spontaneous change in a system that becomes more ordered when that process is exothermic?

When solid sodium acetate crystallizes from a supersaturated solution, can you accurately predict the sign of H for the crystallization? Why or why not?

What is the second law of thermodynamics? For any process, there are four possible sign combinations for Ssys and Ssurr. Which sign combination(s) always give a spontaneous process? Which sign combination(s) always give a non-spontaneous process? Which sign combination(s) may or may not give a spontaneous process?

Through photosynthesis, plants build molecules of sugar containing several carbon atoms from carbon dioxide. In the process, entropy is decreased. The reaction of CO2with formic acid to form oxalic acid provides a simple example of a reaction in which the number of carbon atoms in a compound increases: CO2(aq)+HCOOH(aq)H2C2O4(aq) (a) Calculate the standard entropy change for this reaction and discuss the sign of S . (b) How do plants carry out reactions that increase the number of carbon atoms in a sugar, given the changes in entropy for reactions like this?

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).

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