Concept explainers
When I mole of benzene is vaporized at a constant pressure of 1.00 atm and at its boiling point of 353.0 K, 30.79 kJ of energy (heat) is absorbed and the volume change is +28.90 L. What are ∆E and ∆H for this process?
Interpretation:
Change in enthalpy
Concept introduction:
Internal energy of a system is total energy present in the system. In simple words, it is the sum of kinetic and potential energy of the particles in the system. According to First law of Thermodynamics, Energy of a system is conserved. It is only transferred from one state to another that is from system to surroundings and vice versa. So
Further,
Enthalpy is heat content of the system. The value of enthalpy does not depend on the path of a reaction but depend on state of the system. It has a unique value for each state of the system. Thus, enthalpy is a state function. Enthalpy is represented as,
Enthalpy change, denoted by
Further,
Answer to Problem 131CP
Answer
Change in enthalpy
Change in internal energy
Explanation of Solution
Explanation
Determine
Enthalpy of a system corresponds to amount of heat present in the system. Change in enthalpy is change in the heat content of the system during the course of reaction. That is, heat content of the system either decreases or increases after the completion of the reaction. Endothermic reaction proceeds by absorption of heat that at the end of the reaction, heat content of the system is increased. So the amount of heat absorbed or evolved in the reaction corresponds to the enthalpy change of a reaction.
Calculate the work done, ‘w’.
Using the three equations,
Calculate
‘q’and work done ‘w’ values are calculated in the previous steps. By substituting these values in the equation,
Conclusion
Change in enthalpy
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