thermo f2012

5 kj 42418 kj 30 22015 kj

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Unformatted text preview: h heat is transferred if 36.0 grams of gaseous water is formed from hydrogen and oxygen? Using Hess’ Law •  If the _______ of reacAons equals an overall reacAon, the ΔH of the overall reacAon is the _______ of the ΔH’s of the individual reacAons. •  What is ΔH°rxn for the reacAon H2O(g) + C(graphite) → H2(g) + CO(g) ? •  From reference books we find H2(g) + 1/2 O2(g) → H2O(g) ∆H =  ­242 kJ C(graphite) + 1/2 O2(g) → CO(g) ∆H =  ­111 kJ •  Therefore, H2O(g) + C(graphite) → H2(g) + CO(g) ∆Hrxn° = +131 kJ Given the following data, calculate the ΔH° for 3Fe2O3(s) → 2Fe3O4(s) + ½ O2(g). 2Fe(s) + 3/2 O2(g) → Fe2O3(s) ΔH° = −823 kJ 3Fe(s) + 2 O2(g) → Fe3O4(s) ΔH° = −1120 kJ From heats of formaAon •  FormaAon reacAon: •  How do we know the standard states of the elements? •  ∆Hf° = 0 for elements in their standard states. •  Write the formaAon reacAon for CH3I at 25° C. Using heats of formaAon •  ∆H°rxn = Σ n x ∆Hf° (prod)  ­ Σ n x ∆Hf° (react) 2 CH3OH(g) + 3 O2(g) → 2 CO2(g) + 4 H2O(g) •  ∆H°rxn = [2*∆Hf° (CO2) + 4*∆Hf° (H2O,g)]  ­ [3*∆Hf° (O2) + 2*∆Hf° (CH3OH)] = [2*( ­393.5 kJ) + 4*( ­24...
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This document was uploaded on 03/02/2014.

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