The properties of the solutions which depend on the only number of solute particles but not on the nature of the solute is called colligative properties. Relative lowering in vapor pressure is also an example of colligative properties.
For an experiment sugar solution is prepared for which lowering of vapor pressure was found to be 0.061mm of Hg. ( vapor pressure of water at 20^oC is 17.5m of Hg)
(a) Relative lowering of vapor pressure for the given solution is ___
(b) The vapor pressure (mm of Hg) will be _
(c) Mole fraction of the sugar solution is _________
OR
18 g of glucose, C₆H₁₂O₆ (Molar mass – 180 g mol^-1) is dissolved in 1 kg of water in a sauce pan. At what temperature will this solution boil? (K_b for water = 0.52 K kg mol^-1, boiling point of pure water = 373.15 K)

Question

The properties of the solutions which depend on the only number of solute particles but not on the nature of the solute is called colligative properties. Relative lowering in vapor pressure is also an example of colligative properties.
For an experiment sugar solution is prepared for which lowering of vapor pressure was found to be 0.061mm of Hg. ( vapor pressure of water at 20^oC is 17.5m of Hg)
(a) Relative lowering of vapor pressure for the given solution is ___________
(b) The vapor pressure (mm of Hg) will be _______________
(c) Mole fraction of the sugar solution is _______________
OR
18 g of glucose, C₆H₁₂O₆ (Molar mass – 180 g mol^-1) is dissolved in 1 kg of water in a sauce pan. At what temperature will this solution boil? (K_b for water = 0.52 K kg mol^-1, boiling point of pure water = 373.15 K)

Infinity Learn · Accepted Answer

(a)relative lowering of vapor pressure = $\frac{∆ p}{p^{0}} = \frac{0.061}{17.5} = 0.0035$

(b) $∆ p = p^{0} - p_{s}$

$p_{s} = ∆ p + p^{0}$ =0.061+17.5=17.561 mm of Hg

(c)mole fraction of sugar solution = relative lowering of vapor pressure = 0.0035

OR

$∆ T_{b} = {iK}_{b} m$

$T_{b} = T_{b}^{0} + {iK}_{b} m$

= $373 + (1 \times 0.52 \times \frac{18}{180} \times \frac{1}{1}) = 373.052 K$

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