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Multiple Choice
Calculate ΔH_rxn for the reaction: N2O (g) + NO2 (g) → 3 NO (g) using the following reactions and given ΔH values: 1) 2 NO (g) + O2 (g) → 2 NO2 (g), ΔH = -113.1 kJ; 2) N2 (g) + O2 (g) → 2 NO (g), ΔH = +182.6 kJ; 3) 2 N2O (g) → 2 N2 (g) + O2 (g), ΔH = -163.2 kJ.
A
+74.3 kJ
B
-200.0 kJ
C
+200.0 kJ
D
-74.3 kJ
Verified step by step guidance
1
Identify the target reaction: N2O (g) + NO2 (g) → 3 NO (g). We need to manipulate the given reactions to achieve this target reaction.
Examine the given reactions and their ΔH values: 1) 2 NO (g) + O2 (g) → 2 NO2 (g), ΔH = -113.1 kJ; 2) N2 (g) + O2 (g) → 2 NO (g), ΔH = +182.6 kJ; 3) 2 N2O (g) → 2 N2 (g) + O2 (g), ΔH = -163.2 kJ.
Reverse reaction 1 to get NO2 on the reactant side: 2 NO2 (g) → 2 NO (g) + O2 (g), which changes ΔH to +113.1 kJ.
Use reaction 3 as is, but divide by 2 to match the stoichiometry of N2O in the target reaction: N2O (g) → N2 (g) + 0.5 O2 (g), which changes ΔH to -81.6 kJ.
Combine the modified reactions to form the target reaction: N2O (g) + NO2 (g) → 3 NO (g). Add the ΔH values of the modified reactions to find ΔH_rxn for the target reaction.