Data was collected for TRial 1 to determine the molar mass of a nonvolatile soli

Question

Data was collected for TRial 1 to determine the molar mass of a nonvolatile solid solute when dissolved in cyclohexane. Complete the table for the analysis....

A-freezing point of cyclohexane plus unknown solute

-mass of cyclohexane (g)= 10.14

-mass of added solute (g)= 0.255

Calculate...

If, Kf for cyclohexane (Cxkg/mol)= 20.0 and the Freezing point change, DeltaTf (C)= 3.04

What is the:

a-mass of cyclohexane in solution (g)

b-moles of solute, total (g)

c- mass of solute in solution, total (g)

d- molar mass of solute (g/mol)

Please show me calculations i want to know how to solve it.thanks

Explanation / Answer

a-mass of cyclohexane in solution (g)

-mass of cyclohexane = 10.14 g (given)

b-moles of solute, total (g)

Given, Kf for cyclohexane= 20.0 kg oC/mol

DeltaTf = 3.04oC

We know, delta Tf = Kx m ( where m = molality)

So, 3.04 = 20 x m

m = 0.152m = no. of moles of solute/ mass of solvent in kg

0.152 = no. of moles of solute/ 0.01014

no. of moles of solute = 0.152 x 0.01014 = 1.54128E-3moles

c- mass of solute in solution, total (g)

-mass of added solute = 0.255 g (given)

d- molar mass of solute (g/mol)

no. of moles = mass taken / molar mass

1.54128E-3 mol = 0.255g/ molar mass

molar mass = 0.255/1.54128E-3 = 165.45g/mol

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