A 5.25% solution of a substance is isotonic with a 1.5% solution of urea (molar mass = 60 g mol-1) in the same solvent. If the densities of both the solutions are assumed to be equal to 1.0 g cm-3, molar mass of the substance will be

  • Option 1)

    210.0\: g\: mol ^{-1}

  • Option 2)

    90.0\: g\: mol ^{-1}

  • Option 3)

    115.0\: g\: mol ^{-1}

  • Option 4)

    105.0\: g\: mol ^{-1}

 

Answers (1)

As we learnt in

Isotonic solutions -

Solutions having same osmotic pressures.

- wherein

\pi _{1}= \pi _{2}

C _{1}T _{1}= C _{2}T _{2}

at constant Temp.

C _{1}= C _{2}

 

 C1RT = C2RT

For isotonic solution C1 = C2

\frac{1.6/60}{V}=\frac{5.25/Molecular\ Mass}{V}

M=\frac{5.25\times 60}{1.5}=210

Correct option is 1.

 


Option 1)

210.0\: g\: mol ^{-1}

This is the correct option.

Option 2)

90.0\: g\: mol ^{-1}

This is an incorrect option.

Option 3)

115.0\: g\: mol ^{-1}

This is an incorrect option.

Option 4)

105.0\: g\: mol ^{-1}

This is an incorrect option.

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