Question

Calculate the change in enthalpy (ΔH) for the following reaction at 25°C given the standard enthalpies of formation for each compound: 2H2(g) + O2(g) → 2H2O(g) Standard enthalpies of formation: ΔHf° (H2O)(g) = -241.82 kJ/molΔHf° (H2)(g) = 0 kJ/molΔHf° (O2)(g) = 0 kJ/mol

Answer 1

To calculate the change in enthalpy  H  for the reaction, we can use the following equation:H =  Hf  products  -  Hf  reactants For the given reaction:2H2 g  + O2 g   2H2O g The products are 2 moles of H2O g , and the reactants are 2 moles of H2 g  and 1 mole of O2 g .Using the standard enthalpies of formation provided:H = [2  Hf  H2O  g ] - [2  Hf  H2  g  + Hf  O2  g ]H = [2   -241.82 kJ/mol ] - [2   0 kJ/mol  +  0 kJ/mol ]H =  -483.64 kJ  -  0 kJ H = -483.64 kJThe change in enthalpy  H  for the reaction is -483.64 kJ.