What is ΔG°rxn?

Question

Calculate the ΔG°_rxn using the following information.2 HNO₃(aq) + NO(g) → 3 NO₂(g) + H₂O(l) ΔG°_rxn = ?ΔG°_f (kJ/mol):  -110.9 (2 HNO₃)  87.6 (NO(g))  51.3 (3 NO₂(g))  -237.1 (H₂O(l))

Answer 1

To find ∆Grxn, subtract ∆Gf of reactants from ∆Gf of products.

∆Gf products = (3x51.3) + (-237.1) = 153.9 - 237.9 = -84 kJ (note: ∆Gf NO₂(g) is 51.3 kJ/mol, not per 3 mol)

∆Gf reactants = (2x-110.9) + (87.6) = -221.8 + 87.6 = -134.2

Products - reactants = -84 - (-134.2) = -84 + 134.2

∆Grxn = 50.2 kJ