Question

Calculate the standard enthalpy change for the reaction 2 SO2(g) + O2(g) → 2 SO3(g), given the following standard enthalpy of formation: ΔHf° (SO2) = -296.8 kJ/mol, ΔHf° (SO3) = -396.2 kJ/mol.

Answer 1

To calculate the standard enthalpy change  H  for the given reaction, we can use the equation:H =  [Hf  products ] -  [Hf  reactants ]For the reaction 2 SO2 g  + O2 g   2 SO3 g , we have:H = [2  Hf  SO3 ] - [2  Hf  SO2  + Hf  O2 ]Since O2 is an element in its standard state, its enthalpy of formation is 0 kJ/mol. Therefore, the equation becomes:H = [2   -396.2 kJ/mol ] - [2   -296.8 kJ/mol ]H =  -792.4 kJ  -  -593.6 kJ H = -198.8 kJThe standard enthalpy change for the reaction is -198.8 kJ.