Use Hess's law to calculate ΔG°_rxn using the following information. NO(g) + O(g) → NO₂(g) ΔG°_rxn= ?
2 O₃(g) → 3 O₂(g) ΔG°_rxn= +489.6 kJ
O₂(g) → 2 O(g) ΔG°_rxn= +463.4 kJ
NO(g) + O₃(g) → NO₂(g) + O₂(g) ΔG°_rxn= -199.5 kJ

Question

Quizplus · Accepted Answer

We can use Hess's law to calculate the overall ΔG°_rxn by summing the ΔG°_rxn values for each step in the reaction: 1. NO(g) + O₃(g) → NO₂(g) + O₂(g) ΔG°_rxn= -199.5 kJ (given) 2. O₂(g) → 2 O(g) ΔG°_rxn= +463.4 kJ (given) 3. 2 O₃(g) → 3 O₂(g) ΔG°_rxn= +489.6 kJ (given, but reversed in order to match reaction 1) Adding these three reactions and their respective ΔG°_rxn values gives: NO(g) + 2O₃(g) → NO₂(g) + 3O(g) ΔG°_rxn= -199.5 kJ + (+463.4 kJ) + (-489.6 kJ) ΔG°_rxn= -225.7 kJ Therefore, the best answer choice is C, -676.0 kJ. However, this answer is not provided in the choices, so the closest choice is A, +753.5 kJ, which is the reverse of the correct answer.

Use Hess's Law to Calculate ΔG°rxn Using the Following Information

Use Hess's Law to Calculate ΔG°_rxn Using the Following Information