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 Multiple Choice QuestionsMultiple Choice Questions

271.

Arrange the given compounds in decreasing order of boiling points.

I. CH3CH2CH2CH2Br

II. C(CH3)3Br

III. CH3-CH2-CH(CH3)-Br

  • I > III > II

  • II > I > III

  • I > II > III

  • III > I > II


272.

Two elements A and B form compounds of formula AB2 and AB4. When dissolved in 20.0 g of benzene 1.0 g of AB2 lowers freezing point by 2.3°C whereas 1.0 g of AB4 lowers freezing point by 1.3°C. The Kf for benzene is 5.1. The atomic masses of A and B are

  • 25, 42

  • 42, 25

  • 52, 48

  • 48, 52


273.

The freezing point of a solution containing 0.2 g of acetic acid in 20.0 g benzene is lowered by 0.45°C. The degree of association of acetic acid in benzene is (Assume acetic acid dimerises in benzene and Kf for benzene = 5.12K kg mol-1) Mobserved of acetic acid =  113.78

  • 94.5%

  • 54.9%

  • 78.2%

  • 100%


274.

60 g of urea is dissolved in 1100 g solution. To keep Tf/Kf as 1 mol kg-1 water separated in the form of ice is :

  • 40 g

  • 60 g

  • 100 g

  • 200 g


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275.

Osmosis involved in :

  • excretion of urine

  • interchange of nutrients and waste products betweeen tissue cells and their surroundings

  • in both cases

  • None of the above


276.

Vapour density of PCl5 (g) dissociating into PCl3 (g) and Cl2 (g) is 100. Hence, van't Hoff factor for the case :

PCl5 (g)  PCl3 (g) + Cl2 (g) is :

  • 1.85

  • 3.70

  • 1.085

  • 1.0425


277.

Assertion : Acetone and aniline shows negative deviations.

Reason : H-bonding between acetone and aniline is stronger than that between acetoneacetone and aniline-aniline.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false

  • If both assertion and reason are false.


278.

Which salt is insoluble in water ?

  • NH4Cl

  • KCl

  • Na2SO4

  • NaCl


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279.

Assertion : A solution of sucrose in water is dextrorotatory. But on hydrolysis in the presence of a little hydrochloric acid, it becomes laevorotatory.

Reason : Sucrose on hydrolysis gives unequal amounts of glucose and fructose. As a result of this, change in sign ofrotation is observed.

  • If both assertion and reason are true and reason is the correct explanation of assertion

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.


C.

If assertion is true but reason is false.

The hydrolysis ofsucrose by boiling with a mineral acid (HCl), produces a mixture of equal molecules of D-glucose and D-fructose. Sucrose solution is dextrorotatory, specific rotation = + 66.5°. But on hydrolysis, it becomes laevorotatory. The specific rotation of D-glucose is + 52° and of D-fructose is -92°. Therefore, the net specific rotation of an equimolar mixture of both is :

+52° - 92°2 = 20°


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280.

What happens when chloroform is left open in air in the presence of sunlight?

  • Explosion takes place

  • Phosgene, a poisonous gas is formed.

  • Polymerisation takes place.

  • No reaction takes place.


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