Chapter 4, Problem 4.27NP

Interpretation Introduction

Interpretation:

The change in enthalpy when Cl₂ (g) is heated from 298.15 K to 690 K needs to be calculated.

Concept Introduction:

Based on Kirchhoff's law the change in enthalpy (ΔH) of a reaction is directly proportional to the change in temperature (ΔT) i.e.

  $\begin{array}{l}\text{ΔH α ΔT}\\ {\text{ΔH = C}}_{\text{p}}\text{ΔT}\end{array}$

Since the heat capacity Cp is temperature dependent, the above equation reduces to:

  $\begin{array}{l}{\text{C}}_{\text{p}}{\text{ = (a+bT+cT}}^{\text{2}}{\text{+dT}}^{\text{3}}\text{)}\\ \Delta \text{H = }{\displaystyle \underset{\text{T1}}{\overset{\text{T2}}{\int }}{\text{(a+bT+cT}}^{\text{2}}{\text{+dT}}^{\text{3}}\text{)}}\text{dT ------(1)}\end{array}$

Where a,b, c and d are constants for a particular substance.