You only need to know first is the vapor pressure of water at that boiling point which is ~ 179 mm hg.
So the (vapor pressure of C2H5I = 760 – 179)
And since you know the molecular weight of H2O which is equal to18 g/mol and the molecular weight of C2H5I = 156 g/mol.
Just apply the equation:
grams H2O M.W. H2O ×
P H2O
---------------------- =
-------------------------- = 28.13 grams C2H5I
grams C2H5I M.W. C2H5I
× P C2H5I