[AceTravis]

Ok so I'm really confused on this enthalpy question that I've been working on for the last couple hours. It asks for the  :delta:S of the reaction for the isotopic exhange reaction : H₂O + D₂0 = 2HDO ... I need to express the answer in J/molK . I know I need to use the formula S = k_bln(W) and basically the only thing I don't have is W.

Here is a hint my professor gave us in finding W:

"  I want you to use the Boltzmann entropy formula S = k_b ln (W) for this problem, where you assume that the only thing that is different between H2O, D2O and HOD is the statistics of where the hydrogens are. How many ways can I stick D/H atoms on the two "bonds" to make H2O?   D2O?   HOD? "

Any suggestions would be greatly appreciated. I'm completely lost here.

Travis