Question

Calculate the enthalpy change for the reaction: 2H2 (g) + O2 (g) → 2H2O (l) given that the standard enthalpy of formation for water is -285.8 kJ/mol, and standard enthalpies of formation of H2 (g) and O2 (g) are 0 kJ/mol.

Answer 1

To calculate the enthalpy change for the reaction, we can use the following formula:H_reaction =  H_f products  -  H_f reactants where H_f is the standard enthalpy of formation.For the given reaction:2H2  g  + O2  g   2H2O  l The standard enthalpy of formation for water  H2O  is -285.8 kJ/mol, and for H2  g  and O2  g  it is 0 kJ/mol.H_reaction = [2   -285.8 kJ/mol ] - [2   0 kJ/mol  + 1   0 kJ/mol ]H_reaction =  -571.6 kJ  -  0 kJ H_reaction = -571.6 kJThe enthalpy change for the reaction is -571.6 kJ.