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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3so015

A $2.00 M$ aqueous urea solution (molar mass $60 g mo l^{- 1}$ ) has density $1.03 g m L^{- 1}$ ( $M$ of water $= 18$ ). Which of the following statements are correct?

AThe solution contains $910 g$ of water per litre of solution
BThe molality of urea is approximately $2.20 m$
CThe mole fraction of urea is approximately $0.038$
DThe mass percentage of urea is approximately $6.0%$

Answer: A, B, C

Per litre: mass

1030 g

, urea

120 g

, water

910 g

(true). Molality

= 2/0.910 = 2.198 m

(true). Water

= 910/18 = 50.56 mol

, so

x = 2/ (2 + 50.56) = 0.0381

(true). Mass percent

= 120/1030 \times 100 = 11.65%

, not

6.0%

. Answer: 1, 2 and 3.

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