엥겔의 물리화학 3판 ch4.doc

Chapter 4: Thermochemistry Problem numbers in italics indicate that the solution is included in the Student’s Solutions Manual Questions on Concepts Q4.1) Under what conditions are H and U for a reaction involving gases and/or liquids or solids identical H = U + (PV). H U for reactions involving only liquids or solids because, to a good approximation, the volume does not change as a result of the reaction. If gases are involved, (PV) = nRT. Therefore, H U if the number of moles of reactants and products that are gases are the same. Q4.2) If for the chemical compounds involved in a reaction are available at a given temperature, how can the reaction enthalpy be calculated at another temperature The reaction enthalpy can be calculated to high accuracy at another temperature only if the heat capacities of all reactants and products are known using If the heat capacities of reactants and products are similar, the reaction enthalpy will not vary greatly over a limited …
…