Fe2O3(s) + 2 Al(s) ⟶ Al2O3(s) + 2 Fe(s)
Step 1: We first need to convert ΔH˚ from kJ to J:
ΔH°rxn = –851800 J/mol
**heat is released to the surroundings
Step 2: We can use the following equation to solve for ΔS˚rxn:
Note that we need to multiply each S˚ by the stoichiometric coefficient since S˚ is in J/mol • K.
ΔS°rxn = –10.2 J/mol • K
Step 3: Now that we have ΔH˚rxn and ΔS˚rxn, we can now solve for ΔG˚rxn.
“Thermite” reactions have been used for welding metal parts such as railway rails and in metal refining. One such thermite reaction is Fe2 O3(s) + 2Al(s) ⟶ Al2 O3(s) + 2Fe(s). Is the reaction spontaneous at room temperature under standard conditions? During the reaction, the surroundings absorb 851.8 kJ/mol of heat.
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