The mole fraction of a solvent in aqueous solution of a solute is 0.8. The molality \left ( in\: \: \: mol\: Kg^{-1} \right )  of the aqueous solution is : 

 


 

  • Option 1)

    13.88\times 10^{-2}

  • Option 2)

    13.88\times 10^{-3}

  • Option 3)

    13.88\times 10^{-1}

     

  • Option 4)

    13.88

Answers (1)

 

Mole Fraction -

It is ratio of moles of solute or moles of solvent to moles of solution.

- wherein

If a substance ‘A’ dissolves in substance ‘B’ and their number of moles are n_{A} and n_{B} respectively; then the mole fractions of A and B are given as

Mole fraction of A = (number of moles of A)/(number of moles of solution ) = n_{A}/(n_{A}+ n_{B})

 

 

 

 

We have,

mole\: \: fraction=0.8

X_{solvent}=\frac{n_{solvent}}{n_{solute}+n_{solvent}}=\frac{0.8}{1}

n_{solute}=0.2mole

molality=\frac{0.2}{0.8\times 18}\times 1000

                     =13.88

 


Option 1)

13.88\times 10^{-2}

Option 2)

13.88\times 10^{-3}

Option 3)

13.88\times 10^{-1}

 

Option 4)

13.88

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