Calculate the G°rxn using the following information. 2 HNO3(aq) +NO(g) 3 NO2(g) + H2O(1) AG°rn =7 AH°f (kJ/mol) -207.0 91.3 33.2 -285.8 S°J/mol K 146.0 210.8 240.1 70.0 -151 kJ -85.5 kJ +50.8 kJ +222 kJ -186 kJ

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.)

Coal is used as a fuel in some electric-generating plants. Coal is a complex material, but for simplicity we may consider it to be a form of carbon. The energy that can be derived from a fuel is sometimes compared with the enthalpy of the combustion reaction: C(s)+O2(g)CO2(g) Calculate the standard enthalpy change for this reaction at 25C. Actually, only a fraction of the heat from this reaction is available to produce electric energy. In electric generating plants, this reaction is used to generate heat for a steam engine, which turns the generator. Basically the steam engine is a type of heat engine in which steam enters the engine at high temperature (Th), work is done, and the steam then exits at a lower temperature (Tl). The maximum fraction, f, of heat available to produce useful energy depends on the difference between these temperatures (expressed in kelvins), f = (Th Tl)/Th. What is the maximum heat energy available for useful work from the combustion of 1.00 mol of C(s) to CO2(g)? (Assume the value of H calculated at 25C for the heat obtained in the generator.) It is possible to consider more efficient ways to obtain useful energy from a fuel. For example, methane can be burned in a fuel cell to generate electricity directly. The maximum useful energy obtained in these cases is the maximum work, which equals the free-energy change. Calculate the standard free-energy change for the combustion of 1.00 mol of C(s) to CO2(g). Compare this value with the maximum obtained with the heat engine described here.

Athletic trainers use instant ice packs that can be cooled quickly on demand. Squeezing the pact breaks an inner container, allowing two components to mix and react. This reaction makes the pack become cold. Describe the heat flow for this spontaneous process.

The decomposition of ozone, O3, to oxygen, O2, is an exothermic reaction. What is the sign of q? If you were to touch a flask in which ozone is decomposing to oxygen, would you expect the flask to feel warm or cool?

9.20 State the first law of thermodynamics briefly in your own words.

Sodium reacts violently with water according to the equation Na(s) + H2O() NaOH(aq) + H2(g) Without doing calculations, predict the signs of rH and rS for the reaction. Verify your prediction with a calculation.

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

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?

Which of the following processes will lead to a decrease in the internal energy of a system? (1) Energy is transferred as heat to the system; (2) energy is transferred as heat from the system; (3) energy is transferred as work done on the system; or (4) energy is transferred as work done by the system. (a) 1 and 3 (b) 2 and 4 (c) 1 and 4 (d) 2and3