Exam 17: Thermodynamics: Spontaneous and Nonspontaneous Reactions and Processes

Which of the following statements is/are correct? A large negative free-energy change for a reaction means that ________ I. the equilibrium constant for the reaction is large. II. the equilibrium constant for the reaction is small. III. the reaction greatly favors formation of the products. IV. only a small amount of product is produced at equilibrium.

Which of the processes A-D will lead to a positive change in the entropy of the system?

One of the following statements A-D may be incorrect. If so, identify it.

Which of the relationships between the free-energy change of a system and associated entropy changes is true?

Given the following data relevant to the combustion of ethanol, determine the free energy of formation for liquid ethanol, C₂H₅OH. (C₂H₅OH, l)930.7 kJ/mol (CO₂, g)394.4 kJ/mol (H₂O, g)105.6 kJ/mol

Give an example of a spontaneous and a nonspontaneous chemical process and the sign of the entropy change for the universe for each.

The dissolution of ammonium nitrate in water is a spontaneous endothermic process. It is spontaneous because the system undergoes ________

If for a given chemical reaction at 298 K, both the change in free energy, G, and the change in the standard free energy, G , are positive with G G , then ________

Draw a graph of entropy versus temperature for a typical substance. Be sure to clearly label phases and phase transitions on the graph.

Which of the following figures illustrates best the sequence of the free-energy values (shown with the star) for a chemical reaction at equilibrium to the removal of products, followed by the response of the equilibrium to this stress?

Nitrogen monoxide molecules can react to form dinitrogen oxide and nitrogen dioxide. Determine the equilibrium constant for this reaction under standard conditions from the following data and note whether the reaction is product-favored or reactant-favored.G(NO, g)  86.6 kJ/molG(N₂O, g)  104.2 kJ/molG(NO₂, g)  51.3 kJ/mol

Some pure metals can be obtained from their ores simply by heating to a high temperature to drive off the oxygen, but iron ore usually is refined by reacting it with carbon monoxide. Use the information in the following table to determine whether or not iron ore could be refined by heating to a high temperature and, if so, how high the temperature must be. The oxidation reaction producing iron ore is given below. Thermodynamic Properties

Which of the listed perturbations would change the value of the equilibrium constant for the following reaction? List those that do as a sequence of letters, for example, ACE. NH₄CO₂NH₂(s) 2NH₃(g)  CO₂(g)

What is a microstate and how are microstates quantitatively related to entropy?

Indicate which of the following has the smallest standard molar entropy (S).

Which of the following processes is/are reversible in the thermodynamic sense? I. Iron in the open air rusts. II. NaCl is dissolved in water and then recovered by the evaporation of the water. III. The ice in a mixture of ice and water at 0C and 1 atm melts.

In a biochemical reaction, A  B  C with  30 kJ/mol. Which of the following reactions might be effectively coupled to this reaction so that it becomes more spontaneous? I.C  D  B  E  40 kJ/mol II.C  D  B  E  40 kJ/mol

At what temperature does the Fe(s) Fe(g) phase transition occur?H  415.5 kJ/mol; S  153.4 J/mol · K.

An ice cube at 0C melts in a swimming pool at 25C. What is the change in the entropy of the universe as a result? The ice cube was 2.00 inches on a side. Assume ice has a density of 0.917 g/cm³ and that the enthalpy of fusion of water is 6.01 kJ/mol.

Determine the value of G for the reaction at 298 K. Given