as per the given question, volume of hydrogen/volume of deuterium=8/2=4/1.............(i) By graham's law of diffusion,we have rate of diffussion of hydrogen/rate of diffussion of deuterium=1.414/1 .............(ii) from (i) and (ii),we get that composition to be 4 X 1.414/1 X1=5.656/1 please rate me if satisfied...........