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10.46 Discuss the effect of temperature change on the spontaneity of the following reactions at 1 atm.
(a)
(b)
(c)
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Chapter 10 Solutions
Chemistry for Engineering Students
- Enthalpy changes often help predict whether or not a process will be spontaneous. What type of reaction is more likely to be spontaneous: an exothermic or an endothermic one? Provide two examples that support your assertion and one counterexample.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_forwardThe 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?arrow_forward
- How is the sign of q, heat, defined? How does it relate to the total energy of the system?arrow_forwardWould the amount of heat absorbed by the dissolution in Example 5.6 appear greater, lesser, or remain the same if the heat capacity of the calorimeter were taken into account? Explain your answer.arrow_forwardSolid 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?arrow_forward
- Calculate the standard Gibbs free-energy change when SO3 forms from SO2 and O2 at 298 K. Why is sulfur trioxide an important substance to study? (Hint: What happens when it combines with water?)arrow_forwardA green plant synthesizes glucose by photosynthesis, as shown in the reaction: 6CO2(g) + 6H2O(l) C6H12O6(s) + 6O2(g) Animals use glucose as a source of energy: C6H12O6(s) + 6O2(g) 6CO2(g) + 6HO2(l) If we were to assume that both of these processes occur to the same extent in a cyclic process, what thermodynamic property must have a nonzero value?arrow_forwardCoal 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_forward
- When vapors from hydrochloric acid and aqueous ammonia come in contact, they react, producing a white cloud of solid NH4C1 (Figure 18.9). HCI(g) + NH3(g) NH4Cl(s) Defining the reactants and products as the system under study: (a) Predict whether S(system), S(surroundings), S(universe), rH, and rG (at 298 K) are greater than zero, equal to zero, or less than zero; and explain your prediction. Verify your predictions by calculating values for each of these quantities. (b) Calculate the value of Kp for this reaction at 298 K.arrow_forwardWhat determines Ssurr for a process? To calculate Ssurr at constant pressure and temperature, we use the following equation: Ssurr = H/T. Why does a minus sign appear in the equation, and why is Ssurr inversely proportional to temperature?arrow_forwardDetermine whether each of the following statements is true or false. (a) An exothermic reaction is spontaneous. (b) When G° is positive, the reaction cannot occur under any conditions. (c) S° is positive for a reaction in which there is an increase in the number of moles. d) If H° and S° are both negative, G° will be negative.arrow_forward
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