Question

What are the changes in enthalpy, entropy, and free energy for the hydrogenation of C2H4 to C2H6, and C3H6 to C3H8 at 25 degrees C.

Answer 1

C2H4(g) + H2(g) ---> C2H6(g)

dH^orxn = dH^oproducts - dH^oreactants

            = (-84.68) - (52.25)

            = -136.93 kJ/mol

dS^orxn = dS^oproducts - dG^oreactants

            = (229.6) - (219.45 + 130.684)

            = -120.534 J/K.mol

dG^orxn = -136.93 - (298 x -0.120534)

            = -95.011 kJ/mol

C3H6(g) + H2(g) ---> C3H8(g)

dH^orxn = dH^oproducts - dH^oreactants

            = (-104.5) - (20.2)

            = -124.7 kJ/mol

dS^orxn = dS^oproducts - dG^oreactants

            = (269.9) - (266.9 + 130.684)

            = -127.684 J/K.mol

dG^orxn = -124.7 - (298 x -0.127684)

             = -86.65 kJ/mol