Chapter 9, Problem 123CP

Interpretation Introduction

Interpretation: The value of q in an isothermal expansion of an ideal gas against a constant external pressure needs to be determined. The credibility of statement that for isothermal expansion of an ideal gas against a constant pressure, ΔT = 0 so q = 0 needs to be identified.

Concept Introduction: At constant volume the change in heat for a system to change the internal energy is represented as ΔE or q_V. At constant pressure the change in heat for a system to change the enthalpy is represented as ΔH or q_p. From the first law of thermodynamic:

  $\begin{array}{l}\text{ΔE = q + w }\\ \text{Here:}\\ \text{q = heat}\\ \text{w = work}\\ \text{ΔE=Internal energy}\end{array}$