Free Objective Test 02 Practice Test - 11th and 12th
Question 1
Which of the followings is correct –
SOLUTION
Solution : B
a) △Hmix > 0, △ V mix > 0 are true for mixtures showing positive deviations from Raoult's law only. Hence option (a) is incorrect
b) It is truec) Nitric acid and water forms intermolecular H-bonding. Hence shows Negative deviation from Raoult's law.
d) Azeotropes are of two types – minimum and maximum boiling azeotropes. Only minimum boiling Azeotrope boils at temperature below the boiling temperature of its constituents. Hence option (d) is incorrect.
Question 2
A non-ideal solution was prepared by mixing 30 ml chloroform and 50 ml acetone. The volume of mixture will be
SOLUTION
Solution : B
Chloroform and Acetone solution shows negative deviation from Rault’s law.
Hence △V mix <0
Question 3
Which of the followings is a colligative property
SOLUTION
Solution : A
Only Osmotic pressure is a colligative property.
‘Relative lowering of vapour pressure of the solvent’ is a colligative property but not only vapour pressure. Similar argument for boiling point and freezing point
Question 4
The relative lowering of vapour pressure produced by dissolving 71.5 g of a substance in 1000 g of water is 0.00713. The molecular weight of the substance will be
SOLUTION
Solution : A
△P1P01=n2n1+n2≈n2n1=W2/M2W1/M1
M2=W2×M1W1×(△P1P01)=71.5×181000×0.00713=180.5 g/mole
Question 5
Given that △ Tf if is the diperssion in freezing point of the solvent of non-volatile solute of molality m, the quantity lim m →0(△ Tfm) is equal to
SOLUTION
Solution : D
△Tf =Kf m
limm→0(△Tfm)=limm →0(Kf)=Kf
Question 6
In an experiment on depression of freezing point, two beakers leveled as A and B were filled with 1000 g. of water each. 40 g and 80 g of a certain non-electrolytic solute were added to both the beakers and freezing point of the solutions were noted as TfA and TfB respectively. Now both the solutions were poured into an empty beaker C and the freezing point of the mixed solution is found to be TfC . What is the ratio TfA : TfB : TfC?
SOLUTION
Solution : B
△Tf=Kf m
⇒0−Tf=Kf m
⇒=−Kf m
If 40 g of solute contains 'x'~moles of it then 80 g of the solut ill contains '2x' moles of it
mA=xWt.of solvent in g1000=x10001000=x
mB=2xWt.of solvent in g1000=x10001000=2x
mC=3xWt.of solvent in g1000=3x10001000=1.5x
Required ration TfA:TfB:Tfc=1.2:1.5=2:4:3
Question 7
Which of the following solutions in water will have the lowest vapour pressure
SOLUTION
Solution : B
Depression in vapor pressure is a colligative property. More the no. of particles present in the solution lower will be the vapor pressure. consists of maximum ions hence it show lowest vapour pressure.
MoleculeNaClNa3Po4BaCl2SucroseNo. of ions per molecule1+1 = 23+1 = 41+2 = 31
Question 8
Osmotic pressure of a solution containing 0.1 mole of solute per litre at 273K is (in atm)
SOLUTION
Solution : A
Osmotic pressure ,π=CRT=nVRT=0.11×0.08205× 273 atm
Question 9
A solution of urea contains 8.6 gm/litre (mol. Wt. 60.0). It is isotonic with a 5% (W/W) solution of a non-volatile solute having density 1 g/cc. The molecular weight of the solute will be
SOLUTION
Solution : A
Isotonic solutions have same osmotic pressure
As Osmotic pressure = C R T
⇒ C1=C2
⇒ n1V1=n2V2
5% W/W solution means 100g of solution contains 5 g of solute
∴ 8.6601=5M1001000
⇒ M=5×60×108.6=348.8
Question 10
Two isotonic solutions must have ----
SOLUTION
Solution : D
For two solutions to be isotonic only requirement is that their osmotic pressures should be same. There are no conditions on solutes and solvents.
Question 11
If α is the degree of dissociation of Na2SO4, the vant Hoff's factor (i) used for calculating the molecular mass is
SOLUTION
Solution : C
Na2SO41−α⇌2Na+2α+SO2−4α
Total no. of ions after dissociation = 1+2α
vant Hoff's factor, i=No.of particles after dissociationNo.of particles before dissociation=1+2α
Question 12
A 0.001 molal solution of [Pt(NH3)4cl4] in water had a freezing point depression of 0.0054∘. If Kf for water is 1.80, the correct formulation for the above molecule is
SOLUTION
Solution : D
△T=i Kf m
⇒ i=△TfKf m=0.00541.80×0.001=3
Thus complex produces three ions per molecule. hence possible correct formula is
[Pt(NH3)4Cl2]Cl2
Question 13
A solution containing 30 gms of non-volatile solute in exactly 90 gm water has a vapour pressure of 21.85 mm Hg at 250C. Further 18 gms of water is then added to the solution. The resulting solution has a vapour pressure of 22.15 mm Hg at 250C. Calculate the molecular weight of the solute.
74.2
75.6
67.83
78.7
SOLUTION
Solution : C
Question 14
The average osmotic pressure of human blood is 7.8 bar at 370C. What is the concentration of an aqueous NaCl solution that could be used in the blood stream
0.16 mol/L
0.32mol/L
0.60mol/L
0.45mol/L
SOLUTION
Solution : B
Question 15
Boiling point of chloroform was raised by 0.323 K, when 0.5143 g of anthracene was dissolved in 35 g of chloroform. Molecular mass of anthracene is(= 3.9 kg mol-1)
79.42 g/mol
132.32 g/mol
177.42 g/mol
242.32 g/mol
SOLUTION
Solution : C