Q20 / 90 · JEE Main 2024 (06 Apr Shift 2) · Chemistry

Molality ( \(\mathrm{m}\) ) of \(3 \mathrm{M}\) aqueous solution of \(\mathrm{NaCl}\) is : (Given : Density of solution \(=1.25 \mathrm{~g} \mathrm{~mL}^{-1}\), Molar mass in \(\mathrm{g} \mathrm{mol}^{-1}: \mathrm{Na}-23, \mathrm{Cl}-35.5\))

  • A
    \(1.9 \mathrm{~m}\)
  • B
    \(3.85 \mathrm{~m}\)
  • Correct answer
    C
    \(2.79 \mathrm{~m}\)
  • D
    \(2.90 \mathrm{~m}\)

Solution

3 moles are present in 1 litre solution $\text {molality }=\frac{3 \times 1000}{1.25 \times 1000-[3 \times 58.5]}=2.79 \mathrm{~m}$

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

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