The vapour density of undecomposed N2O4 is 46. When heated, vapour density decreases to 24.5 due to its dissociation to NO2. The percent dissociation of N2O4 at the final temperature is:
1. 87
2. 60
3. 40
4. 70
The molal depression constant for water=1.85 deg/molal and for benzene is 5.12 deg/molal. If the ratio of the latent heats of fusion of benzene to water is 3:8, calculate the freezing point of benzene.
1. 6.75
2. 5.12
3. 8.97
4. 6.1
The Ksp (25) of sparingly soluble salt XY2(s) is 3.56X10-5(mol lit-1)3 and at 30 the vapour pressure of its saturated solution in water is 31.78 mm Hg. Calculate the enthalpy change of the reaction.
Given: Vapour pressure of pure water=31.82 mm Hg
1. 42.5 kJ/mol.
2. 32.1 kJ/mol.
3. 24.5 kJ/mol.
4. 52.5 kJ/mol.
The latent heat of vapourisation of water is 540 cal g-1 at 100. Kb for water is
1. 0.56 K.mole-1
2. 1.86 K.mole-1
3. 0.51 K.mole-1
4. 5.12 K.mole-1
The depression in the freezing point of water when 10 g of CH3CH2CHClCOOH is added to 250 g of water is -Ka=1.4 X 10-3, Kf=1.86K kg mol-1
1. 0.15
2. 2.15
3. 1.15
4. 0.65
The ratio of the vapour pressure of a solution to the vapour pressure of the solvent is
1. Equal to the mole fraction of the solvent
2. Proportional to the mole fraction of the solute
3. Equal to the mole fraction of the solute
4. None of the above
pH of a 0.1 (M) monobasic acid is 2. Osmotic pressure at a given temperature T is-
1. 0.1RT
2. 0.11RT
3. 1.1RT
4. 0.01RT
The vapour pressure of toluene is 59.1 torr at 313.75 K and 298.7 torr at 353.15 K. Calculate, the molar heat of vaporisation.
1. 37888 J mol-1
2. 27188 J mol-1
3. 12834 J mol-1
4. 571328 J mol-1
The vapour pressure of a pure liquid solvent A is 0.80 atm. When a non-volatile substance B is added to the solvent, its vapour pressure drops to 0.60 atm.
Mole fraction of the component B in the solution is:
1. | 0.50 | 2. | 0.75 |
3. | 0.40 | 4. | 0.25 |
A 2.0% solution by weight of urea in water shows a boiling point elevation of 0.18 deg [Molecular weight of urea=60]. Calculate the latent heat of vaporization per gram of water.
1. 495.3 cal/g
2. 560.3 cal/g
3. 525.8 cal/g
4. 501.3 cal/g
A solution of 18 g of glucose in 1000 g of water is cooled to -0.2 oC. The amount of ice separating out from this solution is -
[Kf(H2O) = 1.86 K molal-1]
1. | 70 g | 2. | 140 g |
3. | 90 g | 4. | 210 g |
One molal solution of a carboxylic acid in benzene shows the elevation of boiling point of 1.518 K. The degree of association for dimerisation of the acid in benzene is
(Kb for benzene = 2.53 K kgmol-1)
(1) 60%
(2) 70%
(3) 75%
(4) 80 %
Solution A & B are formed by dissolving a certain amount of glucose and sucrose in water. The Vapour pressure of these solutions is 660 and 560 mm Hg respectively at 100oC. The ratio of molality of solutions A & B will be:-
Saturated solution of Ag2SO4 shows 0.003K rise in boiling point, Ksp will be :(Kb = 5 K kg mol-1)(1m=1M)
1. 3.2 x 10-11
2. 3.2 x 10-10
3. 3.2 x 10-9
4. 3.2 x 10-12
If partial pressure of oxygen is 0.5 atm and KH = 1.4 × 10-3 M/atm, then the amount of oxygen dissolved in 100 ml water at 298K is-
1. | 22.4 mg | 2. | 22.4 g |
3. | 2.24 g | 4. | 2.24 mg |
What amount of CaCl2(i=2.47) is dissolved in 2L water so that its osmotic pressure is 0.5 atm at 27:-
(1) 13.42 g
(2) 19.24 g
(3) 8.834 g
(4) 1.820 g
At 100°C the vapour pressure of a solution of 6.5 g of a solute in 100 g water is 732 mm. If Kb = 0.52, the boiling point of this solution will be
(1) 100°C
(2) 102°C
(3) 103°C
(4) 101°C
The boiling point of 0.2 mol kg-1 solution of X in water is greater than equimolal solution
of Y in water. Which one of the following statements is true in this case?
1. X is undergoing dissociation in water
2. Molecular mass of X is greater than the molecular mass of Y
3. Molecular mass of X is less than the molecular mass of Y
4. Y is undergoing dissociation in water while X undergoes no change
The equivalent conductance of M/32 solution of a weak monobasic acid is 8.0 mho cm2 and at infinite
dilution is 400 mho cm2 .The dissociation constant of this acid is.
1. 1.25x10-5
2. 1.25x10-6
3. 6.25x10-4
4. 1.25x10-4
0.5 molal aqueous solution of a weak acid (HX) is 20% ionised. If Kf for water is 1.86 K kg mol-1, the lowering in freezing point of the solution is:
(1) -1.12 K
(2) 0.56 K
(3) 1.12 K
(4) - 0.56 K
The molar heat of vapourization of toluene is AHv. If its vapour pressure at 315 K is 60 torr & that at 356K is300 torr then AHv = ? (log 2 = 0.3)
(1) 37.5 kJ/mole
(2) 3.75 kJ/mole
(3) 37.5 J/mol
(4) 3.75 J/mole
Relative decrease in vapour pressure of an aqueous solution containing 2 moles [Cu(NH3)3Cl) Cl in 3 moles H2O is 0.50. On reaction with AgNO3, this solution will form (assuming no change in degree of ionisation of substance on adding AgNO3)
(1) 1 mol AgCl
(2) 0.25 mol AgCl
(3) 0.5 mol AgCl
(4) 0.40 mol AgCl
The vapour pressure of pure benzene and toluene are 160 and 60 torr respectively. The mole fraction of toluene in vapour phase in contact with an equimolar solution of benzene and toluene is -
1. | 0.50 | 2. | 0.6 |
3. | 0.27 | 4. | 0.73 |
The vapour pressure of a solvent decreases by 10 mm of mercury when a non-volatile solute was added to the solvent. The mole fraction of the solute in the solution is 0.2. What should be if the decrease in vapour pressure is to be 20 mm of mercury then the mole fraction of the solvent is [CBSE PMT 1998]
(1) 0.8
(2) 0.6
(3) 0.4
(4) None
The molal freezing point constant for water is 1.86°C/m. Therefore, the freezing point of 0.1 m NaCl solution in water is expected to be [MLNR 1994]
(1) –1.86°C
(2) –0.186°C
(3) –0.372°C
(4) +0.372°C