Molality of solution=massofsolventmolesofsolute×1000
Number of moles NaCl=58.529.25=0.5
Number of moles of MgCl2=9519=0.2
NaCl=51.750.5×1000
MgCl2=51.750.2×1000
(ΔTb)=(i1m1)+(i2m2)kb
ΔTb= Elevation in boiling point
i=Van't Hoff factor
m = molality
kb = molal elevation constant
ΔTb=(51.752×0.5×1000×51.753×0.2×1000)×0.52
=16.077
Boiling point of sea water
=116.077∘C
≈116∘C (Nearest integer)