Given:
(a) Determine the standard free energy of formation,
(b) How does your calculated result compare to the value in Appendix G? Explain
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Chemistry: Atoms First
- 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) 2and3arrow_forwardAt 298 K, the standard enthalpies of formation for C2H2(g) and C6H6(l) are 227 kJ/mol and 49 kJ/mol, respectively. a. Calculate H for C6H6(l)3C2H2(g) b. Both acetylene (C2H2) and benzene (C6H6) can be used as fuels. Which compound would liberate more energy per gram when combusted in air?arrow_forwardThe formation of aluminum oxide from its elements is highly exothermic. If 2.70 g Al metal is burned in pure O2 to give A12O3, calculate how much thermal energy is evolved in the process (at constant pressure).arrow_forward
- 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?arrow_forwardThe 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?arrow_forward9.68 What are some features of petroleum that make it such an attractive fuel?arrow_forward
- 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.arrow_forwardWrite the balanced chemical equation for the combustion of methane, CH4(g), to give carbon dioxide and water vapor. Explain why it is difficult to predict whether S is positive or negative for this chemical reaction.arrow_forwardA pot of cold water is heated on a stove, and when the water boils, a fresh egg is placed in the water to cook. Describe the events that are occurring in terms of the zeroth law of thermodynamics.arrow_forward
- 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) 286arrow_forwardThe enthalpy change for the following reaction is 393.5 kJ. C(s,graphite)+O2(g)CO2(g) (a) Is energy released from or absorbed by the system in this reaction? (b) What quantities of reactants and products are assumed? (c) Predict the enthalpy change observed when 3.00 g carbon burns in an excess of oxygen.arrow_forward9.53 Using these reactions, find the standard enthalpy change for the formation of 1 mol of PhO(s) from lead metal and oxygen gas. PbO(s)+C(graphite)Pb(s)+CO(g) H = 106.8 kJ 2C(graphite)+O2(g)2CO(g) H= -221.0 kJ If 250 g of lead reacts with oxygen to form lead(II) oxide, what quantity of thermal energy (in kJ) is ahsorhed or evolved?arrow_forward
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