Molality and Mole Fraction of Urea | JEE Mains Previous Year Question
Q. Molality of an aqueous solution of urea is 4.44 m. Mole fraction of urea in solution is x × 10⁻³, Value of x is ________. (Integer answer)
Step 1: Assume mass of solvent

Let mass of water = 1 kg Molality = moles of urea per kg of solvent

Step 2: Calculate moles of urea

Molality = 4.44 m So, moles of urea = 4.44 mol

Step 3: Calculate moles of water

Moles of water = 1000 / 18 = 55.56 mol

Step 4: Calculate mole fraction of urea

Mole fraction of urea = moles of urea / (moles of urea + moles of water)

= 4.44 / (4.44 + 55.56) = 4.44 / 60 = 0.074

Step 5: Convert into x × 10⁻³ form

0.074 = 74 × 10⁻³

Final Answer: 74

Previous Year Questions

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Updated for JEE Main 2026: This PYQ is important for JEE Mains, JEE Advanced and other competitive exams. Practice more questions from this chapter.

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