Entropy change on heating

Worked example

3.6 mol of a substance (Cₚ = 116 J K⁻¹ mol⁻¹) is heated at constant pressure from 302 K to 194 °C. Find ΔS.

1. 1. Entropy change on heating: solve for ΔS

   $\Delta S = nC_p\ln\dfrac{T_2}{T_1}$

   = 182.2 J K⁻¹

Answer: ΔS = 182 J K⁻¹

Method

ΔS = nCₚ ln(T₂/T₁), with both temperatures in kelvin (a ratio of Celsius values is meaningless).

Formulas used

• Entropy change on heating

  $\Delta S = nC_p\ln\dfrac{T_2}{T_1}$

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