The boiling point of 0.2 mol kg-1 solution of X in water is greater than the equimolal solution of Y in water. Which one of the following statements is true is this case?
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X is undergoing dissociation in water
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The molecular mass of X is greater than the molecular mass of Y.
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Molecular mass of X is less than the molecular mass of Y,
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Y is undergoing dissociation in water while X undergoes no change.
A.
X is undergoing dissociation in water
Molality of solution X = molality of solution Y = 0.2
we know that elevation in the boiling point( ΔTb ) of a solution is proportional to the molal concentration of the solution i.e.
ΔTb = Kbm
where, m is the molality of the solution and Kb is molal boiling point constant or ebullioscopic constant.
therefore,
By elevation in boiling point relation
ΔTb = iKbm or ΔTb directly proportional to i
where i is van't Hoff is a factor
Since ΔTb of solution X is greater than ΔTb of solution Y.
(observed colligative property is greater than normal colligative property).
therefore, i of solution > i of solution Y
therefore solution X undergoing dissociation.
