1. The problem statement, all variables and given/known data All solutions are (aq). In the reaction: HCl + NaOH → NaCl + H2O, ΔH = 60.4 kJ/mol In the reaction: CH3COOH + NaOH → CH3COONa + H20, ΔH = 51.9 kJ/mol In the reaction: CH3COOH + NH4OH → NH4CH3COO + H20, ΔH = 51.6 kJ/mol In the reaction: HCl + NH4OH → NH4Cl + H20, determine ΔH 2. Relevant equations Hess's Law: ΔH(reaction) = ƩΔH(products) - ƩΔH(reactants) ΔH1 = ΔH(NaCl) + ΔH(H2O) - ΔH(HCl) - ΔH(NaOH) ΔH2 = ΔH(CH3COONa) + ΔH(H2O) - ΔH(CH3COOH) - ΔH(NaOH) ΔH3 = ΔH(NH4CH3COO) + ΔH(H2O) - ΔH(CH3COOH) - ΔH(NH4OH) ΔH4 = ΔH(NH4Cl) + ΔH(H2O) - ΔH(HCl) - ΔH(NH4OH) 3. The attempt at a solution I've never quite understood how this works. All of our previous examples were like 2X + Y = 2B, and had a variation of all three variable in each equation. I think I understand it, and start the problem and 30 seconds later realise I don't understand it at all. I don't see how to make the connection between the first three reactions and the fourth. Please help.