JEE Main 2026 — Apr 5, Shift 1 — Chemistry solution

JEE Main2026Apr 5, Shift 1Chemistry

What is the mole fraction of water in 10% by weight (w/w) of aqueous urea solution ?

[Given : Molar mass of H, O, C and N are 1, 16, 12 and 14 g mol $^{- 1}$ respectively]

Solution

Take 100 g of solution: 10 g urea and 90 g water. Molar masses are 60 (urea) and 18 (water).

Moles of urea $= \frac{10}{60} = \frac{1}{6}$ ; moles of water $= \frac{90}{18} = 5$ .

$x_{H_{2} O} = \frac{5}{5 + 1/6} = \frac{30}{31} \approx 0.967$ .

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