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JEE Main 2019 · 12 Jan · Shift II

JEE Main 2019 Chemistry question on Solutions

8 g of NaOH is dissolved in 18 g of H2OH_2O. Mole fraction of NaOH in solution and molality (in mol kg−1kg^{-1}) of the solution respectively are
  1. A.
    0.2, 11.11
  2. B.
    0.167, 22.20
  3. C.
    0.2, 22.20
  4. D.
    0.167, 11.11
Show answer and solution

Correct option: D

Solution

Moles of NaOH = 8/40 = 0.2 mol; moles of H₂O = 18/18 = 1 mol.

Mole fraction of NaOH = 0.2/(0.2 + 1) = 0.2/1.2 = 0.167.

Molality = moles of solute / kg of solvent = 0.2 mol / 0.018 kg = 11.11 mol kg⁻¹.

[JEE Main 2019 · 12 Jan · Shift II]

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