Hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH) to form sodium chloride (NaCl) and water. If ΔH ° = −56.13 kJ/mol and ΔS ° = 79.11 J/mol ⋅ K, what is the temperature of the reaction if ΔG ° = −80.89 kJ/mol?

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

Shown below is a diagram depicting the enthalpy change of a chemical reaction run at constant pressure. a Is the reaction exothermic or endothermic? b What is the sign of H? c What is the sign of q? d If the reaction does no work, what is the sign of E for this process?

How is the sign of q, heat, defined? How does it relate to the total energy of the system?

Calculate H for the reaction N2H4(l)+O2(g)N2(g)+2H2O(l) given the following data: Equation H(KJ) 2NH3(g)+3N2O(g)4N2(g)+3H2O(l) 1010 N2O(g)+3H2(g)N2H4(l)+H2O(l) 317 2NH3(g)+12O2(g)N2H4(l)+H2O(l) 143 H2(g)+12O2(g)H2O(l) 286

The process of dissolving ammonium nitrate, NH4NO3, in water is an endothermic process. What is the sign of q? If you were to add some ammonium nitrate to water in a flask, would you expect the flask to feel warm or cool?

The value of G for the reaction 2C4H10(g)+13O2(g)8CO2(g)+10H2O(l) is 5490. kJ. Use this value and data from Appendix 4 to calculate the standard free energy of formation for C4H 10(g).

The combustion of methane can be represented as follows: a. Use the information given above to determine the value of H for the combustion of methane to form CO2(g) and 2H2O(l). b. What is Hf for an element in its standard state? Why is this? Use the figure above to support your answer. c. How does H for the reaction CO2(g) + 2H2O (1) CH4(g) + O2(g) compare to that of the combustion of methane? Why is this?

9.96 Most first aid "cold packs" are based on the endothermic dissolution of ammonium nitrate in water: NH4NO3(s)NH4+(aq)+NO3(aq) H= 25.69 kJ A particular cold pack contains 50.0 g of NH4NO3 and 125.0 g of water. When the pack is squeezed, the NH4NO3dissolves in the water. If the pack and its contents are initially at 24.0°C, what is the lowest temperature that this bag could reach? (Assume that the ammonium nitrate solution has a specific heat of 4.25J g-l K-l, and that the heat capacity of the bag itself is small enough to be neglected.)

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.