Question

What is the standard enthalpy change for the reaction 2SO2(g) + O2(g) → 2SO3(g) at 25°C and 1 atm pressure, given the following enthalpy of formation values: ΔfH°[SO2(g)] = -296.8 kJ/mol, ΔfH°[O2(g)] = 0 kJ/mol, and ΔfH°[SO3(g)] = -395.72 kJ/mol?

Answer 1

To calculate the standard enthalpy change for the reaction, we can use the formula:H reaction  =  fH products  -  fH reactants For the given reaction, 2SO2 g  + O2 g   2SO3 g , we have:H reaction  = [2  fH SO3 ] - [2  fH SO2  + fH O2 ]Given the enthalpy of formation values:fH[SO2 g ] = -296.8 kJ/molfH[O2 g ] = 0 kJ/molfH[SO3 g ] = -395.72 kJ/molSubstitute these values into the equation:H reaction  = [2   -395.72 ] - [2   -296.8  + 0]H reaction  =  -791.44  -  -593.6 H reaction  = -197.84 kJ/molSo, the standard enthalpy change for the reaction 2SO2 g  + O2 g   2SO3 g  at 25C and 1 atm pressure is -197.84 kJ/mol.