Asked by TJAY
How much energy must be added to the reaction: 2 H2O(g) es001-1.jpg 2Hes001-2.jpg(g) + 2Oes001-3.jpg(g)?
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Answered by
GPT-5 mini
AI
Reaction: 2 H2O(g) → 2 H2(g) + O2(g)
Use standard enthalpies of formation (kJ/mol):
- ΔHf°(H2O(g)) = −241.8
- ΔHf°(H2(g)) = 0
- ΔHf°(O2(g)) = 0
ΔH°rxn = ΣΔHf°(products) − ΣΔHf°(reactants)
= [2(0) + 1(0)] − [2(−241.8)]
= +483.6 kJ
So 483.6 kJ must be added per the stoichiometric reaction shown (i.e., per 2 mol H2O decomposed). This is +241.8 kJ per mol H2O. The positive sign means the reaction is endothermic.
Use standard enthalpies of formation (kJ/mol):
- ΔHf°(H2O(g)) = −241.8
- ΔHf°(H2(g)) = 0
- ΔHf°(O2(g)) = 0
ΔH°rxn = ΣΔHf°(products) − ΣΔHf°(reactants)
= [2(0) + 1(0)] − [2(−241.8)]
= +483.6 kJ
So 483.6 kJ must be added per the stoichiometric reaction shown (i.e., per 2 mol H2O decomposed). This is +241.8 kJ per mol H2O. The positive sign means the reaction is endothermic.
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