5.7 The second and third laws of thermodynamics  (Page 3/7)

What is the difference between Δ S , Δ S °, and $\text{Δ}{S}_{298}^{°}$ for a chemical change?

Calculate $\text{Δ}{S}_{298}^{°}$ for the following changes.

(a) ${\text{SnCl}}_4(l)⟶{\text{SnCl}}_4(g)$

(b) ${\text{CS}}_2(g)⟶{\text{CS}}_2(l)$

(c) $\text{Cu}(s)⟶\text{Cu}(g)$

(d) ${\text{H}}_2\text{O}(l)⟶{\text{H}}_2\text{O}(g)$

(e) $2{\text{H}}_2(g)+{\text{O}}_2(g)⟶2{\text{H}}_2\text{O}(l)$

(f) $2\text{HCl}(g)+\text{Pb}(s)⟶{\text{PbCl}}_2(s)+{\text{H}}_2(g)$

(g) $\text{Zn}(s)+{\text{CuSO}}_4(s)⟶\text{Cu}(s)+{\text{ZnSO}}_4(s)$

Determine the entropy change for the combustion of liquid ethanol, C ₂ H ₅ OH, under standard state conditions to give gaseous carbon dioxide and liquid water.

Determine the entropy change for the combustion of gaseous propane, C ₃ H ₈ , under standard state conditions to give gaseous carbon dioxide and water.

“Thermite” reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite reaction is ${\text{Fe}}_2{\text{O}}_3(s)+2\text{Al}(s)⟶{\text{Al}}_2{\text{O}}_3(s)+2\text{Fe}(s).$ Is the reaction spontaneous at room temperature under standard conditions? During the reaction, the surroundings absorb 851.8 kJ/mol of heat.

Using the relevant $S_{298}^{°}$ values listed in Appendix G , calculate $S_{298}^{°}$ for the following changes:

(a) ${\text{N}}_2(g)+3{\text{H}}_2(g)⟶2{\text{NH}}_3(g)$

(b) ${\text{N}}_2(g)+\frac{5}{2}{\text{O}}_2(g)⟶{\text{N}}_2{\text{O}}_5(g)$

From the following information, determine $\text{Δ}{S}_{298}^{°}$ for the following:

$\text{N}(g)+\text{O}(g)⟶\text{NO}(g)\text{Δ}{S}_{298}^{°}=?$

${\text{N}}_2(g)+{\text{O}}_2(g)⟶2\text{NO}(g)\text{Δ}{S}_{298}^{°}=\text{24.8 J/K}$

${\text{N}}_2(g)⟶2\text{N}(g)\text{Δ}{S}_{298}^{°}=\text{115.0 J/K}$

${\text{O}}_2(g)⟶2\text{O}(g)\text{Δ}{S}_{298}^{°}=\text{117.0 J/K}$

By calculating Δ S _univ at each temperature, determine if the melting of 1 mole of NaCl( s ) is spontaneous at 500 °C and at 700 °C.
$S_{\text{NaCl}(s)}^{°}=72.11\frac{\text{J}}{\text{mol·K}}{S}_{\text{NaCl}(l)}^{°}=95.06\frac{\text{J}}{\text{mol·K}}\text{Δ}{H}_{\text{fusion}}^{°}=\text{27.95 kJ/mol}$

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 reactions listed in [link] . All are run under standard state conditions and 25 °C.

Use the standard entropy data in Appendix G to determine the change in entropy for each of the reactions listed in [link] . All are run under standard state conditions and 25 °C.