Using data from this chapter, calculate the change inenergy expected for each of the following processes.
a.
b.
c.
d.
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Chemical Principles
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- In the reaction of two moles of gaseous hydrogen and one mole of gaseous oxygen to form two moles of gaseous water vapor, two moles of products are formed from three moles of reactants. If this reaction is done at 1.01 104 Pa (and at 0 C), the volume is reduced by 22.4 L. (a) In this reaction, how much work is done on the system (H2, O2, H2O) by the surroundings? (b) The enthalpy change for this reaction is 483.6 kJ. Use this value, along with the answer to (a), to calculate rU, the change in internal energy in the system.arrow_forwardxplain why aluminum cans make good storage containers for soft drinks. Styrofoam cups can be used to keep coffee hot and cola cold. How can this be?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
- High-quality audio amplifiers generate large amounts of heat. To dissipate the heat and prevent damage to the electronic components, heat-radiating metal fins are used. Would it be better to make these fins out of iron or aluminum? Why? (See Table 7- l for specific heat capacities.)arrow_forwardNitromethane, CH3NO2, can be used as a fuel. When the liquid is burned, the (unbalanced) reaction is mainly CH3NO2(l) + O2(g) CO2(g) + N2(g) + H2O(g) a. The standard enthalpy change of reaction (Hvan ) for the balanced reaction (with lowest whole-number coefficients) is 1288.5 kJ. Calculate Hf0 for nitromethane. b. A 15.0-L flask containing a sample of nitromethane is filled with O2 and the flask is heated to 100.C. At this temperature, and after the reaction is complete, the total pressure of all the gases inside the flask is 950. torr. If the mole fraction of nitrogen (nitrogen) is 0.134 after the reaction is complete, what mass of nitrogen was produced?arrow_forwardWhen 1.000 g of gaseous butane, C4H10, is burned at 25C and 1.00 atm pressure, H2O(l) and CO2(g) are formed with the evolution of 49.50 kJ of heat. a Calculate the molar enthalpy of formation of butane. (Use enthalpy of formation data for H2O and CO2.) b Gf of butane is 17.2 kJ/mol. What is G for the combustion of 1 mol butane? c From a and b, calculate S for the combustion of 1 mol butane.arrow_forward
- The 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_forward9.26 Gas furnaces have achieved impressive efficiency levels largely through the addition of a second heat exchanger that condenses water vapor that would otherwise escape out the exhaust system attached to the furnace. How does this process improve efficiency?arrow_forward
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