The relative lowering of vapour pressure of an aqueous solution c

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 Multiple Choice QuestionsMultiple Choice Questions

81.

The relation between solubility of a gas in liquid at constant temperature and external pressure is stated by which law?

  • Raoult's law

  • van't Hoff- Boyle's law

  • van't Hoff- Charles' law

  • Henry's law


82.

Identify the compound amongst the following of which 0.1 M aqueous solution has highest boiling point.

  • Glucose

  • Sodium chloride

  • Calcium chloride

  • Ferric chloride


83.

Freezing point of an aqueous solution is -0.186°C. If the values of Kb and Kf of water are respectively 0.52 K kg mol-1 and 1.86 K kg mol-1 then the elevation of boiling point of the solution in K is

  • 0.052

  • 0.52

  • 1.04

  • 1.34


84.

The correct order of boiling points of 2, 2-dimethylpropane, 2-methylbutane and n-pentane is

  • n-pentane > 2, 2-dimethylpropane > 2-methylbutane

  • n-pentane > 2-methylbutane >  2, 2-dimethylpropane

  • 2, 2-dimethylpropane > 2-methylbutane > n-pentane 

  • 2-methylbutane > 2, 2-dimethylpropane > n-pentane 


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85.

he amount of solute (molar mass 60 g mol-1) that must be added to 180 g of water so that the vapour pressure· of water is lowered by 10%, is

  • 30g

  • 60g

  • 120g

  • 12g


86.

An 1% solution of KCl (I), NaCl (II), BaCl2 (III) and urea (IV) have their osmotic pressure at the same temperature in the ascending order (molar masses of NaCl, KCl, BaCl2 and urea are respectively 58.5, 74.5, 208.4 and 60 g.mol-1). Assume 100% ionization of the electrolytes at this temperature.

  • III < IV < I < II

  • I < III < II < IV

  • III < I < II < IV

  • I < III < IV < II


87.

The difference between the boiling point and freezing point of an aqueous solution containing sucrose (molecular wt = 342g mol-1) in 100 g of water is 105.0°C. If kf and kb of water are 1.86 and 0.51 K kg mol-1 respectively, the weight of sucrose in the solution is about?

  • 34.2 g

  • 342 g

  • 7.2 g

  • 72 g


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88.

The relative lowering of vapour pressure of an aqueous solution containing non-volatile solute is 0.0125. The molality of the solution is

  • 0.70

  • 0.50

  • 0.60

  • 0.80


A.

0.70

According to Raoult's law, Relative lowering of vapour pressure α mole fraction of solute Thus, mole fraction of solute = 0.0125
Mole fraction of a solute is related to the molality by the following expression. 

  1X-1= 1000mB × mwhere, X = mole fraction of solute mB= molecular weight of solvent m = molality 10.0125-1= 100018×mm=12.51-0.0125×18   =12.517.775   = 0.70


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89.

If the elevation in boiling point of a solution of 10g of solute (mol. wt. = 100) in 100g of water is Tb, the ebullioscopic constant of water is 

  • 10

  • 100 Tb

  • Tb

  • 10 Tb


90.

The two isomers X and Y with the formula Cr(H2O)5ClBr2 were taken for experiment on depression in freezing point. It was found that one mole of X gave depression corresponding to 2 moles of particles and one mole of Y gave depression due to 3 moles of particles. The structural formulae of X and Y respectively are

  • [Cr(H2O)4Br2]Cl·H2O; [Cr(H2O)5Cl]Br2 

  • [Cr(H2O)5Cl]Br2;[Cr(H2O)4ClBr]Br·H2O

  • [Cr(H2O)5Cl]Br2;[Cr(H2O)4Br2]Cl·H2O

  • [Cr(H2O)5Cl]Br2;[Cr(H2O)3ClBr2·H2O]


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