16.3 The Second and Third Laws of Thermodynamics

Calculate $\Delta S °$ for the following changes.

(a) $\text{SnCl}_{4} \left(l\right) \rightarrow \text{SnCl}_{4} \left(g\right)$

(b) $\text{CS}_{2} \left(g\right) \rightarrow \text{CS}_{2} \left(l\right)$

(c) $\text{Cu} \left(s\right) \rightarrow \text{Cu} \left(g\right)$

(d) $\text{H}_{2} \text{O} \left(l\right) \rightarrow \text{H}_{2} \text{O} \left(g\right)$

(e) $2 \text{H}_{2} \left(g\right) + \text{O}_{2} \left(g\right) \rightarrow 2 \text{H}_{2} \text{O} \left(l\right)$

(f) $2 \text{HCl} \left(g\right) + \text{Pb} \left(s\right) \rightarrow \text{PbCl}_{2} \left(s\right) + \text{H}_{2} \left(g\right)$

(g) $\text{Zn} \left(s\right) + \text{CuSO}_{4} \left(s\right) \rightarrow \text{Cu} \left(s\right) + \text{ZnSO}_{4} \left(s\right)$

Determine the entropy change for the combustion of gaseous propane, C₃H₈, under the standard conditions to give gaseous carbon dioxide and water.

Using the relevant $S °$ values listed in Appendix G, calculate $\left(\Delta S °\right)_{298}$ for the following changes:

(a) $\text{N}_{2} \left(g\right) + 3 \text{H}_{2} \left(g\right) \rightarrow 2 \text{NH}_{3} \left(g\right)$

(b) $\text{N}_{2} \left(g\right) + \frac{5}{2} \text{O}_{2} \left(g\right) \rightarrow \text{N}_{2} \text{O}_{5} \left(g\right)$

By calculating ΔS_univ at each temperature, determine if the melting of 1 mole of NaCl(s) is spontaneous at 500 °C and at 700 °C.
$S_{\text{NaCl} \left(s\right)}^{\circ} = 72.11 \frac{\text{J}}{\text{mol}\cdot\text{K}} S_{\text{NaCl} \left(l\right)}^{\circ} = 95.06 \frac{\text{J}}{\text{mol}\cdot\text{K}} \Delta H_{\text{fusion}}^{\circ} = \text{27}.\text{95 kJ}/\text{mol}$

What assumptions are made about the thermodynamic information (entropy and enthalpy values) used to solve this problem?

Use the standard entropy data in Appendix G to determine the change in entropy for each of the following reactions. All the processes occur at the standard conditions and 25 °C.

(a) $\text{C} \left(s ,\text{ graphite}\right) + \text{O}_{2} \left(g\right) \rightarrow \text{CO}_{2} \left(g\right)$

(b) $\text{O}_{2} \left(g\right) + \text{N}_{2} \left(g\right) \rightarrow \text{2NO} \left(g\right)$

(c) $\text{2Cu} \left(s\right) + \text{S} \left(g\right) \rightarrow \text{Cu}_{2} \text{S} \left(s\right)$

(d) $\text{CaO} \left(s\right) + \text{H}_{2} \text{O} \left(l\right) \rightarrow \text{Ca} \left(\text{OH}\right)_{2} \left(s\right)$

(e) $\text{Fe}_{2} \text{O}_{3} \left(s\right) + \text{3CO} \left(g\right) \rightarrow \text{2Fe} \left(s\right) + \text{3CO}_{2} \left(g\right)$

(f) $\text{CaSO}_{4} \cdot \text{2H}_{2} \text{O} \left(s\right) \rightarrow \text{CaSO}_{4} \left(s\right) + \text{2H}_{2} \text{O} \left(g\right)$