We have the equation π=iCRT . As urea is non-electrolyte, i=1,π is the osmotic pressure at temperature T . π1=C1RT1 400=C1R×273K⋅⋅⋅⋅⋅⋅⋅(i) π2=C2RT2 100=C2R×293K⋅⋅⋅⋅⋅⋅⋅(ii) Dividing Eq. (i) by Eq. (ii),
π1
π2
=
400
100
=
C1×273
C2×293
C1
C2
=
400×293
100×273
=4.29 C1 is 4.29 times C2 . So, the dilution factor is 4.3.