Q59 / 180 · COMEDK 2025 (10 May Shift 1) · Chemistry

Choose the correct statement.

  • Correct answer
    A
    For a solvent, $\quad K_b=\dfrac{R \times M_1 \times T_b^2}{1000 \times \Delta \text { Hvap }}$ $\left(\mathrm{R}=\right.$ Gas constant, $M_1=$ Molar mass of solvent, $T_b=B . P$ of the solvent $)$
  • B
    Hypotonic solution is more concentrated with respect to the other solution separated by a semi permeable membrane
  • C
    A 1.0 molal solution of Glucose in water is more concentrated than 1.0 M glucose solution in the same solvent.
  • D
    A solution formed by adding Carbon di-sulphide to Acetone forms a maximum boiling azeotrope.

Solution

(1) Correct: $K_b = \dfrac{R \times M_1 \times T_b^2}{1000 \times \Delta H_{vap}}$ is the standard thermodynamic expression for the ebullioscopic constant, where $R$ is the gas constant, $M_1$ is the molar mass of solvent, $T_b$ is the boiling point of pure solvent, and $\Delta H_{vap}$ is the molar enthalpy of vaporization.

(2) Incorrect: A hypotonic solution has lower solute concentration. The solution with higher concentration is called hypertonic.

(3) Incorrect: 1.0 M solution has 1 mole of glucose in 1 L of solution (less than 1 kg of solvent), while 1.0 m solution has 1 mole in exactly 1 kg of solvent. Hence 1.0 M is more concentrated than 1.0 m, not less.

(4) Incorrect: $CS_2$ + Acetone shows positive deviation from Raoult's law (weaker A-B interactions), forming a minimum boiling azeotrope, not a maximum boiling azeotrope.

The correct statement is (1).

Hence, the correct answer is option: 'A'.

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