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AP EAMCET · Chemistry · Solutions

A \(25 \%\) solution of cane-sugar (molar mass \(=342 \mathrm{~g} \mathrm{~mol}^{-1}\) ) is isotonic with \(5 \%\) solution of a substance \(A\). Then find the molecular weight of \(A\).

  1. A \(6.84 \mathrm{~g} \mathrm{~mol}^{-1}\)
  2. B \(68.4 \mathrm{~g} \mathrm{~mol}^{-1}\)
  3. C \(25 \mathrm{~g} \mathrm{~mol}^{-1}\)
  4. D \(684 \mathrm{~g} \mathrm{~mol}^{-1}\)
Verified Solution

Answer & Solution

Correct Answer

(B) \(68.4 \mathrm{~g} \mathrm{~mol}^{-1}\)

Step-by-step Solution

Detailed explanation

Two solutions are isotonic when they have the same osmotic pressure. It is only possible when they have same molar concentration. A \(25 \%\) solution of cane-sugar means \(100 \mathrm{~g}\) of solution contain \(25 \mathrm{~g}\) of cane-sugar. For dilute solution…