Question

15 gram of unknown molecular material was dissoled in 450 grm of water

Answer 1

ΔTf=0∘−(−0.34∘C)  

=0.34∘Cor0.34K

WB=15.0g

WA=450g

kf=1.86kkgmol−1

Substituting these values in the expression

MB=Kf×WB×1000ΔTf×WA

MB=1.86kkgmol−1×15.0g×1000gkg−10.34k×450g

=182.35gmol−1