Vapour pressure of benzene at 30°C is 121.8 mm. When 15 g of

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 Multiple Choice QuestionsMultiple Choice Questions

311.

Assertion : Addition of NH4OH to an aqueous solution of BaCl2 in the presence of NH4Cl (excess) precipitates Ba(OH)2.

Reason : Ba(OH)2 is insoluble in water.

  • 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.


312.

Assertion : The molecular weight of acetic acid determined by depression in freezing point method in benzene and water was found to be different.

Reason : Water is polar and benzene is non-polar.

  • 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.


313.

Which one of these, is not a colligative property ?

  • vapour pressure

  • osmotic pressure

  • lowering in freezing point

  • Elevation in boiling point


314.

The osmotic pressure of which solution is maximum? (consider that decimormal solution of each is 90% dissociated) :

  • Aluminium sulphate

  • Barium chloride

  • Sodium sulphate

  • A mixture of equal volumes of (b) and (c)


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315.

The mixture ofconcentrated HCl and HNO3 made in 3 : 1 ratio contains

  • ClO2

  • NOCl

  • NCl3

  • N2O4


316.

The average osmotic pressure of human blood is 7.8 bar at 37°C. What is the concentration of an aqueous NaCl solution that could be used in the blood stream?

  • 0.16 mol/L

  • 0.32 mol/L

  • 0.60 mol/L

  • 0.45 mol/L


317.

Which one of the statements given below concerning properties of solutions, describes a colligative effect?

  • Boiling point of pure water decreases by the addition of ethanol.

  • Vapour pressure of pure water decreases by the addition of nitric acid.

  • Vapour pressure of pure benzene decreases by the addition of naphthalene.

  • Boiling point of pure benzene increases by the addition of toluene.


318.

Which one of the following is not a buffer solution?

  • 0.8M H2S + 0.8M KHS

  • 2M C6H5NH2 + 2M C6H5NH3-Br-

  • 3M H2CO3 + 3M KHCO3

  • 0.05M KClO4 + 0.05M HClO4


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319.

In aqueous alkaline solution, two electrons reduction of HO2- gives

  • HO-

  • H2O

  • O2

  • O2-


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320.

Vapour pressure of benzene at 30°C is 121.8 mm. When 15 g of a non-volatile solute is dissolved in 250 g of benzene, its vapour pressure is decreased to 120.2 mm. The molecular weight of the solute is

  • 35.67 g

  • 356.7 g

  • 432.8 g

  • 502. 7 g


B.

356.7 g

Relative lowering of vapour pressure is given by:

                      P°-PP°=w/mw/m +W/M

Where, P°= Vapour pressure of pure solvent

           P = Vapour pressure of solution 

           w = mass of solute

           m = molecular of solute

           W = mass of solvent

           M = molecular mass of solvent

For dilute solution

121.8 - 120.2121.8= 15/m250/78m = 356.265


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