JEE Advanced 2014 · Paper 1 · Chemistry Q39

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ChemistryInteger+3Question 39 of 60

A compound $\ce{H2X}$ with molar weight of 80 g is dissolved in a solvent having density of $0.4\ \mathrm{g\,mL^{-1}}$ . Assuming no change in volume upon dissolution, the molality of a 3.2 molar solution is

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Answer and worked solution

Official answer: 8

Take 1 L of solution. It contains 3.2 mol of $\ce{H2X}$ .

Solvent mass. With no volume change on dissolving, the solvent volume is 1 L, so its mass is $1000\times0.4=400$ g.

Molality.
$m=\frac{3.2}{0.400}=8\ \mathrm{mol\,kg^{-1}}.$

Answer: 8

Topics:Concentration terms

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JEE Advanced 2014 · Paper 1, Chemistry question 39