Question

Calculate the enthalpy change for the reaction: 2H2(g) + O2(g) → 2H2O(l) using Hess's law given the following reactions: 2H2(g) + O2(g) → 2H2O(g)      ΔH1 = -483.6 kJ/mol 2H2O(g) → 2H2O(l)           ΔH2 = -40.7 kJ/mol

Answer 1

To calculate the enthalpy change for the reaction 2H2 g  + O2 g   2H2O l  using Hess's law, we need to add the enthalpy changes of the given reactions.H1 = -483.6 kJ/mol  for the reaction 2H2 g  + O2 g   2H2O g  H2 = -40.7 kJ/mol  for the reaction 2H2O g   2H2O l  Now, we add the enthalpy changes of these two reactions to find the enthalpy change for the desired reaction:H_total = H1 + H2H_total =  -483.6 kJ/mol  +  -40.7 kJ/mol H_total = -524.3 kJ/molSo, the enthalpy change for the reaction 2H2 g  + O2 g   2H2O l  is -524.3 kJ/mol.