I really just need help with a walk through on one trial. I am extremely confuse

Question

I really just need help with a walk through on one trial. I am extremely confused on the steps of finding the solutions. We used Benzopheone which has a FW of 182.22. I would really appreciate if I could get a walk through on the first trial and then I can work the rest!

A melting Point of pure 1,4-Dichlorobenzene (DCB) $3.540 Exact mass of DCB 9.963 Melting Point of DCB/unknown solution-trim 52.549 degree c Exaxt Mass of sample 0.237g Melting Point of DCB/unknown solution trial 51.61 degreeC Average Molar Mass of unknown solute= g/mol

Explanation / Answer

DTf = i*Kf*m

(T0-Ts) = i*Kf*m

m = molality of DCB solution = (0.237/182.27)*(1000/9.963)

     = 0.13 molal

i = vanthoff factor of DCB = 1

Kf = para-dichlorobenzene = 7.10 C/m

trail 1 :

DTf = T0-Ts = 53.540 - 52.549 = 0.991 C

(53.540 - 52.549 ) = 1*7.1*m

m = molality of solution = 0.14 molal

total mass of solute = 0.237 gram

molality = weight of solute / mwt * 1000 / wt of solvent

   0.14 = (0.237 / x)*(1000/9.963)

   x = 169.91 g/mol

molarmass of solute = 169.91 g/mol

no of moles of solute = 0.237/169.91 = 0.0014 mole

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