1
Sri Chaitanya IIT- JEE Academy CHEMISTRY – ASSIGNMENT [Dilute Solution & Colligative Properties]
J.IIT *************************************************************************************** 1.
An azeotropic mixture of two liquids boils at a lower temperature than either of them when 1) it is saturated
2) it does not deviate from Raoult’s law
3) it shows negative deviation from Raoult’s law 4) it shows positive deviation from Raoult’s law 2.
A solution of a substance containing 1.05g per 100ml was found to be isotonic with 3% glucose solution. The molecular weight of the substance is 1) 63
3.
4.
2) 630
3) 6.3
4) 31.5
In cold countries, enthylene glycol is added to water in the radiators of cars during winters. It results in 1) lowering boiling point
2) reducing viscosity
3) reducing specific heat
4) lowering freezing point
Beckmann thermometer measures 1) boiling point of the solution 2) freezing point of the solution 3) any temperature 4) elevation in boiling point or depression in freezing point
5.
6.
When HgI2 is mixed with aqueous solution of KI, then 1) freezing point decrease
2) freezing point does not change
3) freezing point increase
4) boiling point remains unchanges
The freezing point of 0.05 molal solution of a non-electrolyte in water is ______ . Kf = 1.86 k 1) –1.860C
7.
2) – 0.930C
3) – 0.0930C
4) 0.930C
Which of the following 0.1 M aqueous solutions will have the lowest freezing point 1) potassium sulphate 2) sodium chloride
8.
kg mol-1.
3) urea
4) glucose
The V.P. of a dilute solution of a non-volatile solute is P and the V.P. of pure solvent is P0, the lowering of the V.P. is 1) + Ve
2) – Ve
3) P P0
4) P0 P
2
9.
The Vant Hoff factor NaCl assuming 100% dissociation is 1) 1 2
10.
2) 2
2) Hypertonic
3) Hypotonic
4) none
Two solutions A and B are separated through a SPM. A has high O.P then B. The osmosis will occur from 1) A to B
12.
4) 3
The solution in which the blood cells retain their normal form are with regard to the another 1) Isotonic
11.
3) 1
2) B to A
3) Both
4) none
When an ideal binary solution is in equilibrium with its vapour, molar ratio of the two components in the solution and in the vapour phase is 1) same
2) different
3) may or may not be same depending upon volatile nature of the two components 13.
14.
The lowering of vapour pressure of 0.1 M aqueous solution of NaCl, CuSO4 and K2SO4 are 1) all equal
2) in the ratio 1 : 1 : 1.5
3) in the ratio 3 : 2 : 1
4) in the ratio 1.5 : 1 : 2.5
The boiling point of C6H6, C6H5 – NH2, CH3OH and C6H5NO2, are 800C, 1840C, 650C and 2120C respectively. Which has higher vapour pressure at room temperature 1) C6H6
15.
2) CH3OH
3) C6H5NH2
4) C6H5NO2
The correct relationship between the b.pt of very dilute solution of AlCl3 t1 and CaCl2 t 2 having same molar concentration is 1) t1 > t 2
16.
3) t1 = t 2
4) none
The freezing point of equimolal aqueous solutions will be highest for 1) C6H5NH3Cl
17.
2) t 2 > t1
2) Ca(NO3)2
3) La(NO3)3
4) C6H12O6
The relationship between osmotic pressure at 273 K when 10 gm glucose P1 10g urea P2 and 10g sucrose P3 are dissolved in 250ml of water is 1) P1 > P2 > P3
18.
3) P2 > P1 > P3
4) P2 > P3 > P1
In dilute solution the depression in f.pt. is directly proportional to 1) normality
19.
2) P3 > P1 > P2
2) molality
3) molarity
4) mole fraction
A maxima or minima obtained in the temperature composition curve of a mixture of two liquids indicates? 1) An azeotropic mixture
2) a eutectic formation
3) that the liquids are immiscible with one another
3
4) that the liquids are partially miscible at the maximum or minimum 20.
Two solvents A and B have K f values 1.86 and 2.79 K mole-1 kg respectively. A given amount of a substance when dissolved in 500g of A, it completely dimerizes and when same amount of substance is dissolved in 500g of B, the solute undergoes trimerization. What will be the ratio of observed lowering of freezing point in two cases for A and B. 1) 3 : 2
21.
22.
2) 1 : 1
3) 2 : 3
Which inorganic precipitates act as semipermeable membrane 1) calcium phosphate
2) barium oxalate
3) nickel phosphate
4) copper ferrocyanide
By adding water to the solution of ionic compound its? 1) Concentration remains same
2) Concentration increases
3) Ionisation may increases 23.
4) Concentration decreases
The process of getting fresh water from sea water is known as 1) Osmosis
24.
4) 3 : 4
2) Filtration
3) Desaltation
4) Reverse osmosis
Which of the following plots does not represent the behaviour of an ideal binary liquid solution? 1) Plot of PA versus XA (mole fraction A in liquid phase) is linear 2) Plot of PB versus XB is linear 3) Plot of Ptotal versus XA (or XB) is linear 4) Plot of Ptotal versus XA is non linear
25.
Which of the following plots correctly represents the behaviour of an ideal binary liquid solution? 1) Plot of XA (mole fraction of A in liquid phase) versus YA (mole fraction of A in vapour phase) is linear 2) Plot of XA versus YB is linear 3) Plot of 1 X A versus 1 YA is linear 4) Plot of 1 X A versus 1 YB is linear
26.
For an ideal binary liquid solution with PA0 > PB0 , which of the following relations between XA (mole fraction of A in liquid phase) and YA (mole fraction A in vapour phase) is correctly represented? 1) XA = YB
2) XA > YA
3) XA < YA
4) XA and YA cannot be correlated with each other 27.
A binary liquid solution of chloroform and acetone is prepared. Which of the following statements correctly represents the behaviour of this liquid solution? 1) The solution formed is an ideal solution
4
2) The solution formed is non ideal solution with positive deviations from Raoult’s law 3) The solution formed is non ideal solution with negative deviations from Raoults law 4) Chloroform exhibits positive deviation whereas acetone exhibits negative deviation from Raoult’s law 28.
A semi permeable membrane used in the measurement of osmotic pressure of a solution allows the passage of 1) solvent molecules through it
2) solute molecules through it
3) both solvent and solute molecules through it 4) either solvent or solute and not both through it 29.
In which mode of expression the concentration of solution remains independent of temperature 1) Molarity
30.
2) Normality
2) 0.2
2) 0.15 N
3) 0.3 N
2) 200
3) 400
2) N-Phosphoric acid
3) 6g of NaOH/100 ml4) 0.5m H2SO4
Hydrochloric acid solutions A and B have concentrations of 0.5 N and 0.1 N respectively. The volumes of solutions A and B required to make 2 litres of 0.2 NHCl are 1) 0.5lit of A+1.5lit of B
2) 1.5lit of A+0.5lit of B
3) 1.0lit of A+1.0lit of B
4) 0.75lit of A+1.25lit of B
The molarity of pure water is 1) 55.6
37.
4) decrease in % W/W
Which of the following solutions has the highest normality 1) 1.8g of KOH/1 lit.
36.
4) 1000
2) decrease in molarity
3) decrease in mole fraction
35.
4) 0.4 N
Increasing the temperature of an aqueous solution will cause 1) decrease in molality
34.
4) 0.7
A 500g tooth paste sample has 0.2g fluoride concentration. What is the concentration of F in terms of ppm level? 1) 250
33.
3) 0.5
30 ml of solution is neutralized by 15ml of 0.2N base. The strength of the acid solution is 1) 0.1 N
32.
4) Molality
If 0.50 mole of BaCl2 is mixed with 0.20 mole of Na3PO4, the maximum number of moles of Ba3(PO4)2 that can be formed is 1) 0.1
31.
3) Formality
2) 50
3) 100
The mole fraction of water in 20% aqueous solution of H2O2 is
4) 18
5
1) 77 68 38.
2) 87 ml
3) 175 ml
4) 145 ml
3) Osmotic pressure
4) Freezing point
Which of the following is not a colligative property? 1) Osmotic pressure
41.
4) 80 20
Which one is a colligative property? 1) Boiling point 2) Vapour pressure
40.
3) 20 80
Volume of 0.1M K2Cr2O7 required to oxidises 35ml of 0.5M FeSO4 solution is 1) 29 ml
39.
2) 68 77
2) Elevation of b.p.
3) Vapour pressure
4) Depression of f.p.
100ml of a liquid A was mixed with 25ml of a liquid B to give a non-ideal solution of A-B mixture. The volume of this mixture would be 1) 75 ml
2) 125 ml
3) just more than 125 ml
4) close to 125ml but not exceeding 125ml 42.
Which of the following pairs shows a positive deviation from Raoult’s law? 1) Water-hydrochloric acid 3) Acetone-Chloroform
43.
48.
2) 60
3) 600
4) 180
2) 1.026K
3) 10.26K
4) 1.832K
The molal freezing point constant for water is 1.86K Kg/mole. If 342gm of cane sugar (C12H22O11) is dissolved in 1000g of water, the solution will freeze at 1) –1.860C
47.
3) 0.1 M BaCl2 4) 0.1 M MgSO4
The latent heat of vapourisation of water is 9700 cal/mole and if the b.p. is 1000C the ebullioscopic constant of water is 1) 0.513K
46.
2) 0.2 M sucrose
Elevation in boiling point was 0.520C when 6gm of a compound X was dissolved in 100gm of water. Molecular weight of X is (Kb of water is 5.2K per 100g of water) 1) 120
45.
4) Benzene-methanol
Which one of the following solutions would produce maximum elevation in B.P. 1) 0.1 M glucose
44.
2) Water-nitric acid
2) 1.860C
3) –3.920C
4) 2.420C
Which has the minimum freezing point 1) one molal NaCl solution
2) one molal KCl solution
3) one molal CaCl2 solution
4) one molal urea solution
The freezing point of 1 molal NaCl solution assuming NaCl to be 100% dissociated in water is KHO mol-1.
Kf = 1.86
6
1) –1.860C 49.
52.
2) 1 : 2 : 1
3) 1 : 2 : 3
2) 1
3) 0.001
4) 2 : 2 : 3
4) 100
The vapour pressure of a liquid in a closed container depends upon 1) amount of liquid
2) surface area of the container
3) temperature
4) none of the above
The temperature at which the vapour pressure is equal to the external pressure is called the 1) critical temperature
2) boiling point
3) normal point 53.
4) +3.720C
What is the molality of a solution of a certain solute in a solvent if there is a freezing point depression of 0.1840C and the freezing point constant is 18.4. 1) 0.01
51.
3) +1.860C
0.01M solution each of urea, common salt and Na2SO4 are taken, the ratio of depression of freezing point is 1) 1 : 1 : 1
50.
2) –3.720C
4) saturation point
What would happen if a thin slice of sugar beet is placed in a concentrated solution of NaCl 1) Sugar beet will lose water from its cells 2) Sugar beet will absorb water from solution 3) Sugar beet will neither absorb nor lose water 4) Sugar beet will dissolve in solution
54.
The freezing point of the water is depressed by 0.0370C in a 0.01 moles NaCl solution. The freezing point of a 0.02 mol solution of sucrose in 0C is 1) –0.0370
55.
56.
4) –0.1850
1) Temperature is decreased
2) Solution constant is increased
3) Number of solute molecules is increased
4) Volume is increased
Osmotic pressure of sugar solution at 240C is 2.5 atmosphere. The concentration of the solution in gm mole per litre is 2) 1.025
3) 102.5
4) 0.1025
3) Isotonic
4) Normal
Solutions with same osmotic pressure are called 1) Hypertonic
58.
3) –0.0740
The osmotic pressure of solution increases if
1) 10.25 57.
2) –0.0185
2) Hypotonic
Which of the following correctly expresses the Van’t Hoff factor? 1) Calculated osmotic pressure / Observed osmotic pressure
7
2) Observed molecular weight / Calculated molecular weight 3) Calculated boiling point / Observed boiling point 4) Observed colligative property / Calculated colligative property 59.
Van’t Hoff factor for an electrolyte is 1) > 1
60.
2) 60
2) 0.5
2) 87%
3) Trimerization of benzoic acid
2) Dimerisation of benzoic acid 4) Solvation of benzoic acid
2) i = (1+x)
3) i = 1 - x 2
4) i = 1 + x 2
2) BaCl2
3) Al2(SO4)3
4) C12H22O11
2) 0.01 M NaCl 3) 0.01 M C2H5OH
4) 0.008 M MgCl2
2) hypotonic
3) isotonic
4) none
If PA is the vapour pressure of a pure liquid A and the mole fraction of A in the mixture of two liquids A and B is x the partical vapour pressure of A is 1) (1 – x)PA
69.
4) 74%
When two solutions are separated by a semi permeable membrane and there is no flow of the solvent across the membrane, the solutions are said to be 1) hypertonic
68.
3) 100%
The aqueous solution with the lowest freezing point of the following group is 1) 0.01 M MgSO4
67.
4) 2.5
Which of the following solution has osmotic pressure nearer to that equimolar solution of K 4 Fe(CH)6 1) Na2SO4
66.
3) 2
Benzoic acid undergoes dimerisation in benzene solution, the Van’t Hoff factor ‘i’ is related to the degree of association ‘x’ of the acid is 1) i = (1- x)
65.
4) 180
The molecular weight of benzoic acid in benzene as determined by depression in freezing point method corresponds to 1) Ionisation of benzoic acid
64.
3) 120
The Van’t Hoff factor for 0.1M Ba(NO3)2 solution is 2.74. The degree of dissociation is 1) 91.3%
63.
4) none of the above
The ratio of the value of any colligative property for KCL solution to that of sugar solution is nearly 1) 1
62.
3) = 1
Acetic acid dissolved in benzene shows a molecular mass of 1) 30
61.
2) < 1
2) x PA
3) x (1- x)PA
The freezing point depression constant Kf depends on
4) 1- x x PA
8
70.
1) properties of pure solvent
2) properties of pure solute
3) properties of solute and solvent
4) always constant for all solutes and solvents
The most likely of the following mixtures to be an ideal solution is 1) NaCl – H2O
71.
For
2) C2H5- OH – C6H6
3) C7H16(l) – H2O4) C7H16(l) C8H18(l)
CrCl3 .xNH3 , elevation in BP of one molal solution is double of one molal urea solution, hence x is
(complex is 100% ionized) 1) 4 72.
2) 3 58
2) 5.5
3) 2.5
4) none
2) A is hypotonic
3) both 1 and 2 4) none
2) kg mol-1 K
3) K
4) none
1M Glucose solution at TK will have osmotic pressure (S = solution constant) 1) 10ST 4
77.
4) 1 2
Molal elevation constant has unit 1) mol kg-1 K
76.
3) 3 4
Osmosis of A into solution B will take place if 1) A is hyper tonic
75.
4) none of these
Van’t Hoff’s factor for K 3 Fe(CN) 6 (ionization 50%) will be 1) 1
74.
3) 6
“Relative lowering in vapour pressure” of a solution containing one mol. K2SO4 in 54gm H2O is (K2SO4 in 100% ionized) 1) 1 55
73.
2) 5
2) 3 ST
3) 4 ST
4) ST
Mixture of volatile component to A and B has total V.P, P = 254 – 119x (x = mo. Fraction of B) Hence PA0 and PB0 are 1) 135, 254
78.
4) 135, 119
2) 4
3) 6
4) 8
An ideal binary liquid solution, the plot of Ptotal versus XA (mole fraction of liquid A) is linear with slope and intercept equal to 1) PA0 - PB0 , PA0
80.
3) 254, 135
2.56 gm of sulphur in 100gm of CS2 has depression in F.P. of 0.0100 Kf = 0.10 (molal). Hence atomcity of sulphur in CS2 is 1) 2
79.
2) 119, 254
2) PA0 - PB0 , PB0
3) PB0 - PA0 , PA0
4) PB0 - PA0 , PB0
Mole fraction of A vapours above solution in mix of A and B X A = 0.4 will be
9
PA0 100mm, PB0 200mm 1) 0.4 81.
2) 0.8
4) none
If relative decrease in V.P is 0.4 for a solution containing 1 mol. NaCl in 3 mol. H2O, NaCl is ….. % ionised 1) 60%
82.
3) 0.25
2) 50%
3) 100%
4) 40%
1 mol A+ 3 mol B (volatile liquids) PA0 = 300mm, PB0 =100mm , mol fraction of B in vapour state above solution is 1) 0.75
83.
2) 0.25
3) 0.50
Which is true about ideal solutions 1) the change in volume of mixing is zero 3) both 1 and 2
84.
4) 0.8
2) 50 mm
3) 200 mm
4) 300 mm
25 ml of an aqueous solution of KCl was found to require 20 ml of 1 M AgNO3 solution when titrated using a K2CrO4 as indicator.. Depression in freezing point of KCl solution with 100% ionization will be (Kf = 2 for mol –1 Kg and molarity = molality) 2) 0.8
3) 1.6
4) 3.2
12.2gm of benzoic acid (M=122) in 100gm H2O has elevation of boiling point of 0.270. Kb = 0.540 kg/mol. If there is 100% polymerization no. of molecules of benzoic acid in associated state is 1) 1
88.
3) 1.0
Vapour pressure of mixture of above question is
1) 0.4 87.
4) none of these
2) 0.6
1) 125 mm 86.
2) the change enthalpy of mixing is zero
Vapour pressure of A is 100mm and that of B is 200mm, mol. fraction of A in vapour state in the mixture of 3 mol of A and 1 mol of B is 1) 0.4
85.
4) 0.66
2) 2
3) 3
4) 4
Based on the given diagram, which of the following statements regarding the solutions of two miscible volatile liquids are correct? (1)
Plots AD and BC show that Raoult’s law is obeyed for the solution in which B is a solvent and A is the solute and as well as for that in which A is solvent and B is solute
(2)
Plot CD shows that Daltons law of partial pressures is observed by the binary solutions of components A and B
(3)
EF+BG=GH, and AC and BD correspond to the vapour pressures of the pure solvents A and B respectively. Select the correct answer using the codes given below
10
1) 1 and 2 89.
2) 2 and 3
3) 1 and 3
4) 1, 2 and 3
An ideal liquid solution, the plot of 1 X A versus 1 YA (where X A and YA are the mole fractions of A in liquid and vapour phase) is linear with slope and intercept equal to 1)
PB0 - PA0 PA0 , 0 PB0 PB
2)
PB0 - PA0 PB0 , 0 PB0 PA
3)
PA0 PB0 - PA0 , PB0 PB0
4)
PB0 PB0 - PA0 , PA0 PB0
PART – A 1.
The vapour pressure of liquids A and B at 1000C are 3000 mm and 100 mm of Hg respectively. A mixture of two liquids forming ideal solution at 1000C exerts a vapour pressure in gaseous phase in which A and B are one mole each in vapour phase. Calculate the vapour pressure of mixture and the mole fraction of liquid mixture in which two liquids are mixed.
Ans: 1 4, 2.
3 4, 150 mm
A mixture of ethyl alcohol and propyl alcohol has a V.P of 290 mm at 270C. If mole fraction of ethyl alcohol is 0.65. Calculate the vapour pressure of ethyl alcohol, if vapour pressure of propyl alcohol is 210 mm.
Ans: 333 mm 3.
Calculate vapour pressure of a solution at 1000C having 3.42g of cane sugar in 180g water.
Ans: 759.2 mm 4.
What weight of non volatile solute (urea) NH2CONH2 needs to be dissolved in 100g of water in order to decrease the vapour pressure of water by 25%. What will be the molality of solution?
Ans: 18.52 m 5.
An aqueous solution of glucose containing 12g in 100g of water was found to boil at 100.340C. Calculate Kb for water in K mole-1 Kg.
Ans: 0.51 6.
At 00C, 23.54 ml of N2 at a partial pressure of 1 atm will dissolve per litre of water. Under the same conditions, 48.89ml of O2 will dissolve. Calculate the amount by which the freezing point of air free water is lowered by being saturated with air. (composition of air is 79 vol % of N2 and 21 vol % of O2) Kf = 1.86K kg mol-1
Ans: 0.00240C 7.
How much ice will separate if a solution containing 10g of ethylene glycol in 100g of water is cooled to – 100C? Kf for H2O=1.86 K mole-1 kg.
Ans: 70.00 g
11
8.
At 00C vapour pressure of H2O and its solution of 8.49g NaNO3 in 100g water are 4.62 and 4.483mm respectively. Calculate degree of ionization of NaNO3.
Ans: 69.8% 9.
A solution of 0.643g of an organic compound in 50ml of benzene (density 0.879 g/ml) lowered its freezing point from 5.510C to 5.030C. Calculate the molecular weight of solid. Kf for benzene is 5.12 K mole-1 kg..
Ans: 156.06 10.
Calculate the freezing point of an aqueous solution of a non electrolyte having an osmotic pressure 2.0 atm at 300 K. Kf = 1.86 K mole-1 kg and R = 0.0821 litre atm K-1 mol-1.
Ans: - 0.1510C 11.
A 1% KCl solution is ionized to the extent of 82%. What would be its osmotic pressure 180C.
Ans: 5.836 atm 12.
A 5% solution of glucose is isotonic with 1.1% solution of KCl at 300C. Calculate degree of ionization of KCl.
Ans: 88.29% 13.
The vapour pressure of a solution containing 2g of an electrolyte BA in 100g water which dissociates in one B+ and one A – ion in water is 751 mm at 1000C. Calculate degree of ionization of BA if its mol.wt. is 56.
Ans: 86.41 14.
A solution containing 28g phosphorous in 315g CS2 (b.p. 46.30C) boils at 47.980C.K1b for CS2 is 2.34 K mole-1 kg. Calculate m.wt. of phosphorous and deduce its molecular formula. Assume its complete association
Ans: P4 15.
The freezing point of a solution containing 0.2g of acetic acid in 20.0g benzene is lowered by 0.450C. Calculate the degree of association of acetic acid in benzene. Assume acetic acid dimerizes in benzene. Kf for benzene = 5.12 K mole-1 kg
Ans: 94.5 16.
Calculate the molal lowering of vapour pressure for H2O at 1000C.
Ans: 13.68 mm 17.
Calculate the amount of urea in 100ml of a solution at 250C, whose osmotic pressure is 20.4 atm
Ans: 5.0029 18.
Dry air was successively passed through a solution of 5g solute in 80g water and then through pure water. The loss in weight of solution was 2.5g and that of pure water was 0.04g. What is mol.wt. of solute?
12
Ans: 70.31 19.
Calculate the (a) molar concentration and (b) molality of a sulphuric acid solution of density 1.1g cm-3, containing 27 mass percent of sulphuric acid. For what volume should 100ml of this acid be diluted to prepared 1.5N solution
Ans: V = 404.9 ml 20.
A current of dry air was passed through a series of bulbs containing 1.25g of a solute A2B in 50g of water and then through pure water. The loss in weight of the former series of bulbs was 0.98g and in the later series 0.01g. If the molecular weight of A2B is 80, calculate degree of dissociation of A2B. [Ans:40.7 %]
21.
Two elements A and B form compounds having molecular formula AB2 and AB4. When dissolved in 20g of benzene. 1.0g of AB2 lowers of freezing point by 2.30C. Where as 1.0gm of AB4 lowers the freezing point by 1.30C. Calculate the molar masses of A and B. Given : Kf (benzene) = 5.1 kg mol-1.
Ans: 25.6, 42.65 22.
8.057510-2 kg of Glauber’s salt is dissolved in water to obtain 1 dm3 of a solution of density 1077.2 kgm-3. Calculate the molarity, molality and mole fraction of Na2SO4 in the solution.
Ans: 0.25m, 0.24m, 0.0043 23.
Determine the volume of dilute nitric acid (density 1.11g cm-1 19 mass % HNO3). That can be prepared by diluting 50.0 cm3 of concentrated acid (density 1.42g cm g cm-3, 69.8 mass % HNO3). Calculate the molarities and molalities of concentrated and dilute acids.
Ans: 15.73m, 36.67m, 3.35m, 3.72m, v=234.8m 24.
The freezing point of 0.02 mole fraction solution of acetic acid in benzene is 277.4K. Assuming molality equal to molarity, calculate Kc for the equilibrium reaction
T
f
= 278.4 K, K f 5K kg mole-1
Ans: 3.2159 25.
An aqueous solution containing 5% by weight of urea and 10% by weight of glucose. What will be its freezing point? Kf for H2O is 1.86 K mole-1 kg.
Ans: - 3.040 C 26.
Concentrated HNO3 has a specific gravity of 1.42 and is 69 mass % in HNO3, what mass of HNO3 is contained in 300 mL of this rengent? What volume of this concentrated HNO3 be diluted to obtain 800 mL of 0.20 M HNO3?
Ans: 293.94gm
13
27.
If boiling point of an aqueous solution is 100.10C. What is its freezing point? Given latent heat of fusion and vaporization of water are 80 cal g-1 and 540 cal g-1 respectively.
Ans: - 0.3610C 28.
A certain mass of a substance when dissolved in 100g C6H6 lowers the freezing point by 1.280C. The same mass of solute dissolved in 100g of water lowers the freezing point by 1.400C. If the substance has normal molecular weight in benzene and is completely dissociated in water, into how many ions does it dissociate in water? Kf for H2O and C6H6 are 1.86 and 5.12 K mole-1 kg respectively.
Ans: 3 29.
1g of mono basic acid in 100g of water lowers the freezing point by 0.1680. If 0.2g of same acid requires 15.1ml of N/10 alkali for complete neutralization, calculate degree of dissociation of acid. Kf for H2O is 1.86 K mole-1 kg.
Ans: α = 19.6% 30.
To 500 cm3 of water, 310-3 kg of acetic acid is added. If 23% of acetic acid is dissociated. What will be the expression in freezing point? K=1.86 K kg+1 mole-1 and d=0.997 g/cm3.
Ans: 0.229 31.
A tube of uniform cross-sectional area 1 cm2 is closed at one end with semi permeable membrane. A solution of 5gm glucose per 100ml is placed inside the tube and is dipped in pure water at 270C. When equilibrium is established calculated 1) osmotic pressure of solution 2) height developed in vertical column. Assume density of glucose solution 1 gm/ml.
Ans: 6.841 atms, 70.43 m 32.
The molar volume of liquid benzene (d=0.877 g/ml) increases by a factor of 2750 as it vaporizes at 200C and that of liquid toluene (d=0.867 g/ml) increases by a factor of 7720 at 200C. A solution of benzene and toluene at 200C has a vapour pressure of 46, Torr. Find the mole fraction of benzene with vapour above the solution.
Ans: 0.73 33.
A 1.2% solution (wt/volume) of NaCl is isotonic with 7.2% solution (wt/volume) of glucose. Calculate degree of ionization and Vant Hoff factor of NaCl.
Ans: α = 0.95, i = 1.95 34.
What is the ratio by weight of NaF and NaI which when dissolved in water produces the same osmotic effects as 0.1 molar solution of urea in water? The weight of residue obtained on evaporation of the salt solution is 0.48 gm per 100 ml of solution evaporated. Assume complete dissociation of the salts [Ans:0.28]
14
35.
100gm of sucrose solution in water is cooled to –0.50C. What weight of ice would be separated out at this temperature of solution started to freezes at –0.380C? Kf for H2O = 1.86 K mole-1 kg.
Ans: 22.42 gm 36.
Vapour pressure of C6H6 and C7H8 mixture at 500C is given by P(mm Hg)=180 XB+90, where Xb is the mole fraction of C6H6. A solution is prepared by mixing 936g benzene and 786g toluene and if the vapours over this solution is removed and cooled. Calculate the mole fraction in vapour state above the solution
Ans: 0.93 37.
A solution comprising 0.1mol of naphthalene and 0.9mol of benzene is cooled until some benzene freezes out. The solution is then decanted off from the solid and warmed to 353 K. Where its vapour pressure is found to be 670 torr. The freezing and normal boiling point of benzene are 278.5 K and 353 K, respectively and its enthalpy of fusion is 10.67 kJ mol-1. Calculate the temperature to which the solution was cooled originally and the amount of benzene that must have freezen out. Assume conditions of ideal solution.
Ans: 270.39 K 38.
The vapour pressures of two pure liquids A and B that form an ideal solution are 300 and 800 torr, respectively, at temperature T. A mixture of the vapours of A and B for which the mole-fraction of A is 0.25 is slowly compressed at temperature T. Calculate (a)
the composition of the first drop of the condensate
(b)
the total pressure when this drop is formed
(c)
the composition of the solution whose normal boiling point is T.
(d)
the pressure when only the last bubble of vapour remains
(e)
composition of the last bubble
Ans: (a) XA 0.47 39.
(b) 565 Torr (c) X A 0.08 (d) 675 Torr (e) X A 0.11
The density of a 3 molal sodium thiosulphate solution is 1.25g cm-3. Calculate the percentage by mass of sodium thiosulphate, (ii) the mole fraction of sodium thiosulphate, and (iii) molarities of Na+ and S2 O3 2 - ions 1) 42.71
40.
2) 0.051
3) 4.3
4) 2.15
The freezing point of an aqueous solution of KCN containing 0.1892 mol kg-1 was –0.7040C. On adding 0.095 mol. of Hg (CN)2, the freezing point of the solution was –0.5380C. Assuming that the complex is formed according to the equation. Hg(CN) 2 +mCN - Hg(CN) mm+2- . Find the formula of the complex. (Kf = 1.86 K kg mol-1)
Ans: Hg(CN) 4 PART – B
2
15
1.
At 270C two solutions of glucose in water of concentration 0.01M and 0.001M are separated by semipermeable membrane with respect to water. On what solution, pressure need be applied to prevent osmosis? Calculate magnitude of this applied pressure.
Ans: 0.2217 atm 2.
An aqueous solution of glucose boils at 100.010C. The molal elevation constant for water is 0.5 K kg mole-1. What is the number of glucose molecule in the solution containing 100g water.
Ans: 1.2 1021 3.
0.48g of a substance was dissolved in 10.6g C6H6. The freezing point of benzene was lowered by 1.80C. Calculate m.Wt. of substance. Molecular depression constant for benzene is 50 K mole-1 100g.
Ans: 125.79 4.
A 5% by weight solution of cane sugar in water has freezing point of –20C calculate the f.pt. of 5% by weight solution of glucose in water if freezing point of pure water is 00C.
Ans: - 3.80 C 5.
The vapour pressure of an aqueous solution of glucose is 750mm of Hg at 373 K. Calculate molality and mole fraction of solute.
Ans: 0.741 6.
Calculate the relative lowering in V.P. of 10g of a solute (m.wt.100) is dissolved in 180g water
7.
What will be boiling point of bromine when 174.5mg of octa atomic sulphur is added to 78g of Bromine. Kb for Br2 is 5.2 K mole-1 kg and b.pt of Br2 = 332.15 K
Ans: 332.1950 K 8.
A mixture which contains 0.55g of camphor and 0.090g of an organic solute melts at 1610C. The solute contains 93.75%C and 6.25%H by weight. What is the molecular formula of compound K1f for camphor is 37.50 mole-1 kg? The m.pt. of camphor is 2090C.
Ans: C10 H8 9.
Calculate the osmotic pressure of 20% anhydrous CaCl2 solution at 00C assuming 100% ionization.
Ans: 121.15 atm 10.
When 11.7g of NaCl are dissolved in 200g of water the depression in freezing point is doubled than the depression caused by 342g of cane sugar in 1000g of water. From this information what do you infer about the nature of solute particles of NaCl in solution.
Ans: 100%
16
11.
2g of benzoic acid dissolved in 25g of C6H6 shows a depression in freezing point equal to 1.62 K.Molal depression constant of C6H6 is 4.9 K kg mole-1. What is the percentage association of acid if it forms double molecules in solution?
Ans: 99.2% 12.
A sugar syrup of mass 214.2g contains 34.2g of sugar C12 H 22 O11 . Calculate molality, and (ii) mole fraction of sugar in the syrup.
Ans: 0.556 13.
The vapour pressure of pure benzene at a certain temperature is 640mm Hg. A non volatile solid weighing 2.175g is added to 39.0g of benzene. The vapour pressure of the solution is 600mm Hg. What is the molar mass of the solid substance?
Ans: 69.6 14.
A 0.1 molar solution of NaCl is found to be isotonic with 1% urea solution. Calculate (a) Van’t Hoff factor, and (b) degree of dissociation of sodium chloride. Assume density of 1% urea equal to 1g cm-3.
Ans: 1.667 15.
A solution is prepared from 26.7g of an unknown compound and 116.0g of acetone at 313K. The vapour pressure of pure acetone at this temperature is 0.526 atm and that of the acetone above the solution is 0.501 atm. Calculate the molar mass of the unknown compound.
Ans: 267.7 16.
When 2g of a nonvolatile hydrocarbon containing 94.4 percent carbon is dissolved in 100g benzene, the vapour pressure of benzene is lowered from 74.66 Torr to 74.01 Torr. Determine the molecular formula of the hydrocarbon.
Ans: C14 H10 17.
The density of a 3 molal sodium thiosulphate solution is 1.25g cm-3. Calculate the percentage by mass of sodium thiosulphate, (ii) the mole fraction of sodium thiosulphate, and (iii) molarities of Na+ and S2 O3 2 - ions 1) 42.71
18.
2) 0.051
3) 4.3
4) 2.15
What volume of 1.0 MHCl must be added to 50.0 mL of 0.50M HCl to give a solution whose concentration is 0.6 M?
Ans: 12.5 19.
At 1000C, benzene and toluene have vapour pressures of 1357 and 558 Torr, respectively. Assuming these two form an ideal binary solution. Calculate the composition of the solution that boils at 1 atm and 1000C. What is the composition of vapour issuing at these conditions?
17
1) XB = 0.247 20.
2) X1B 0.447
3) X T 0.753
4) XT = 0.553
Calculate osmotic pressure of a solution containing 100ml of 3.4% solution (by volume) of urea (m.wt.60) and 50 ml of 1.6% solution (by volume) of cane sugar (m.wt.342) at 270C.
Ans: 9.704 21.
The molarity of NH3 in an aqueous solution is 11.8 mol dm-3. The density of the solution is 0.916g cm-3. Determine 1) molality 2) mass percent and 3) mole fraction of NH3
Ans: 16.5 mol/kg 22.
What is the mole fraction of benzene in a benzene-toluene solution that is in-equilibrium with a vapour phase containing 60.0 mol % C6H6? Given P (benzene)=95.1 mm Hg and P(toluene)=28.4 mm Hg.
Ans: 0.31 23.
The density of a 3.742M solution of glycerol C3H8O3 in water at 298 K is 1.077g cm-3. The vapour pressure of pure water at this temperature is 23.76 Torr. Calculate the vapour pressure of water above the solution.
Ans: 21 Torr 24.
Chloro acetic acid has K=1.9310-3 M. Calculate the freezing point of 0.1M solution of this acid. Assume that molarity and molality have identical values. Kf (water)=1.86 K kg mol-1.
Ans: - 0.210C 25.
Two liquids A and B form ideal solution at 300K. The vapour pressure of a solution containing one mole of A and four moles of B is 560mm of Hg. At the same temperature. If one mole of B is taken out from the solution, the vapour pressure of solution decreases by 10mm of Hg. Calculate vapour pressures of A and B in pure state.
Ans: 400, 600 mm 26.
How much ice will separate if a solution containing 25g of ethylene glycol in 100g of water is cooled to – 100C? Kf for H2O = 1.86 K mole-1 kg.
Ans: 25.00 g 27.
At 00C vapour pressure of H2O and its solution of 8.49g NaNO3 in 100g water are 4.62 and 4.483 mm respectively. Calculate degree of ionisation of NaNO3.
Ans: 69.8% 28.
How much of concentrated H2SO4 of density 1.84g cm-3 and containing 98 mass percent of H2SO4 must be diluted to prepare 100 cm3 of the 20 mass percent H2SO4 of density 1.14g cm-3?
18
Ans: 12.64m 29.
A solution containing 30g of nonvolatile solute in exactly 90g water has a vapour pressure of 21.85 mm Hg at 250C. Further 18g of water is then added to the solution. The resulting solution has vapour pressure of 22.18 mm Hg at 250C. Calculate (a) molar mass of the solute and (b) vapour pressure of water at 250C.
Ans: 23.99mm Hg 30.
A solution contains 3.22g of HclO2 in 47.0g of water. The freezing point of the solution is 271.10 K. Calculate the fraction of HclO2 that undergoes dissociation to H+ and ClO 2- . Given: Kf (water) = 1.86 K kg mol-1.
Ans: α = 0.02 31.
The addition of 3g of a substance to 100g CCl4 (M = 154g mol-1) raises the boiling point of CCl4 by 0.600C. If Kb (CCl4) is 5.03 K.mol-1 kg, calculate (a) the freezing point depression, (b) the relative lowering of vapour pressure, (c) the osmotic pressure at 298K and (d) the molar mass of the substance. Give: Kf (CCl4)=31.8 K kg mol-1 and P(solution)=1.64g cm-3.
Ans: 4.669 atm, mw 251 Ans: 112.7 PASSAGES I.
Consider following law for the solution of a gas in a solvent and answer the questions at the end of it. “The solubility of a gas in a liquid is directly proportional to the pressure of the gas”.
1.
Select correct statement: 1) NH3 is soluble in water due to hydrogen bonding as well as due to formation of ions 2) Gases which can be liquefied easily are more soluble in water than the gases which cannot be liquefied 3) Both of the above are incorrect
2.
An ionic compound that attracts atmospheric water so strongly that a hydrate is formed is said to be 1) dilute
3.
4) Both of the above are correct
2) hygroscopic
3) immiscible
4) miscible
The solubility of gases in liquids 1) increase with increase in pressure and temperature 2) decreases with increase in pressure and temperature 3) increases with increase in pressure and decrease in temperature 4) decreases with increase in pressure and increase in temperature
4.
The solubility of N2(g) in water exposed to the atmosphere, when the partial pressure is 593 mm is 5.310- 4 M. It solubility at 760mm and at the same temperature is
19
1) 4.110- 4 M II.
2) 6.810- 4 M
3) 1500 M
4) 2400 M
Following statement is considered to define colligative properties: Answer the questions at the end of it.
Properties whose values depend only on the concentration of solute particles in solution and not on the identity of the solute are called colligative properties. 1.
Acetic acid in benzene solution forms dimmer due to intermolecular H-bonding. For this case van’t Hoff factor is 1) i = 1
2.
5.
2) 1.02
3) 1.10
4) 1.20
2) 3
3) 4
4) 5
In which case van’t Hoff factor is maximum? 1) KCl, 50% ionized
2) K2SO4 40% ionized
3) SnCl4, 20% ionized
4) FeCl3, 30% ionized
A complex containing K+, Pt (IV) and Cl – is 100% ionized giving i = 3. Thus, complex is 1) K 2 PtCl 4
III.
4) inclusive
An aqueous solution of 0.01M CH3COOH has van’t Hoff factor of 1.01. If pH = -log H + , pH of 0.01M CH3COOH solution would be 1) 2
4.
3) i < 1
If pKa = - log Ka = 4, and Ka = Cx2 then vant’s Hoff factor for weak monobasic acid when C=0.01 M is 1) 1.01
3.
2) i > 1
2) K 2 PtCl6
3) K 3 PtCl5
4) K PtCl3
Consider following figure and answer the questions at the end of it. Figure explains elevation in boiling point when a non-volatile solute is added to a solvent.
Variation of vapour pressure with temperature and showing elevation in boiling point
1.
Tb is m
Given that Tb is the elevation in boiling point of the solvent in a solution of molality ‘m’ then equal to 1) Kb (molal elevation constant)
2) Lv (latent heat of vaporization)
20
3) S (entropy change) 2.
4) x (mole fraction of solute)
Elevation in b.p. of an aqueous urea solution is 0.520. K b 0.520 mol-1 kg . Hence mole fraction of urea in this solution is 1) 0.982
3.
2) 0.0567
4) 0.018
A complex of iron and cyanide ions is 100% ionized at 1m (molal).
K
b
If its elevation in b.p. is 2.080
= 0.520 mol-1 kg then the complex is
1) K 3 Fe(CN) 6 4.
3) 0.943
3) K 4 Fe(CN)6
2) Fe(CN) 2
4) Fe(CN) 4
Select correct statement: 1) Heats of vaporization for a pure solvent and for a solution are similar because similar intermolecular forces between solvent molecules must be overcome in both cases. 2) Entropy change between solution and vapour is smaller than the entropy change between pure solvent and vapour 3) Boiling point of the solution is larger than that of the pure solvent 4) All are correct statements
5.
Consider following terms: (I) mKb
(II) mKbi
(III)
Tb i
(IV) Kb
Terms which can be expressed in degree (temperature) are 1) III, IV 6.
2) I, II
3) I, II, III
4) I, III
Ratio of Tb K b of 6% AB2 and 9% A2B (AB2 and A2B both are non-electrolytes) is 1 mol/kg in both cases. Hence atomic masses of A and B are respectively. 1) 60, 90
IV.
2) 40, 40
3) 44.5, 9.5
4) 10, 40
Questions at the end are based on following phase diagram for pure solvent and solution for depression in freezing point. Freezing point of a liquid is defined as that temperature at which it is in equilibrium with its solid state.
Phase diagram for a pure solvent and solution for depression in freezing point
21
1.
Freezing point of the following system is:
solid solvent liquid solvent 1) 2.
H - G S
2)
H S
3)
G S
4)
S H
Freezing point of a solution is smaller than that point of a solvent. It is due to 1) H of solution and solvent is almost identical since intermolecular forces between solvent molecules are involved 2) S of the solution is larger than that for the solvent 3) S of the solution is smaller than that of the solvent 4) H of solution is much higher than of solvent but S of solution is smaller than that of the solvent
3.
Select correct statement: 1) Solution has more molecular randomness than a pure solvent has, the entropy change between solution and solid is larger than the entropy change between pure solvent and solid 2) Heats of fusion of solution and solvent are similar since similar forces of intermolecular forces are involved 3) Sugar containing solution freezes at a lower temperature than pure water 4) All are correct statements
4.
60g of urea is dissolved in 1100g solution. To keep T K f as 1 mol/kg, water separated in the form of ice is 1) 40g
V.
2) 60g
3) 100g
4) 200g
Read the following fact and answer the questions at the end of it. Osmosis, like all colligative properties, results from an increase in entropy as pure solvent passes through the membrane and mixes with the solution.
1.
Desalinating of sea water is now done using 1) reverse osmosis
2.
2) osmosis
3) filtration
4) evaporation
Red blood cells are placed in a solution and neither hemolysis nor crenation occurs. Therefore the solution is
1) hypertonic
2) hypotonic
3) isotonic
4) isotropic
22
3.
The passage of a solvent across a semipermeable membrane because of concentration differences is called 1) dialysis
5.
2) hemolysis
3) hydration
4) osmosis
Match the terms with definitions Term I
Definition
:
Hemolysis
A : the shrinking of a red blood cell when placed in a solution of greater osmolarity than the cell itself
II :
Crenation
B :
III :
Hygroscopic
C : refers to a solution having a greater osmolarity than 0.30 osmol, the osmolarity of normal red blood cells
IV :
Hypertonic
D :
V :
Isotonic E : the swelling and bursting of a red blood cell when placed in a solution of lower osmolarity than the cell itself
refers to two solutions of same osmolarity
an ionic compound which attracts water molecules from the
atmosphere
Matching codes are :
VI.
I
II
III
IV
V
1)
A
B
C
D
E
3)
E
D
B
C
A
I
II
III
IV
V
2)
E
D
C
B
A
4)
E
A
D
C
B
Read the following statement and answer the questions at the end of it. The partial vapour pressure of any volatile component of an ideal solution is equal to the vapour pressure of the pure component multiplied by the mole fraction of that component in the solution.
1.
At a given temperature, total vapour pressure in Torr of a mixture of volatile components A and B is given by P=120-75 XB hence vapour pressure of pure A and B respectively in Torr. 1) 120, 75
2.
2) 120, 195
3) 120, 45
4) 75, 45
A mixture contains 1 mol. volatile liquid A ( p 0 A = 100 mm Hg) and 3 mol volatile liquid B ( p 0 B = 80 mm Hg). If solution behave ideally, total vapour pressure of the distillate is approximately: 1) 85mm Hg
3.
2) 86mm Hg
3) 90mm Hg
4) 92mm Hg
Moles of K2SO4 to be dissolved in 12 mol. water to lower its vapour pressure by 10mm Hg at a temperature at which vapour pressure of pure water is 50mm Hg is 1) 3 mol
2) 2 mol
3) 1 mol
4) 0.5 mol
23
VII.
Answer the questions (given below) which are based on the following diagram. Vapour pressure plots of benzene-toluene mixtures at 200C. Solutions of benzene and toluene are ideal. Raoult’s law is valied for both components over the entire range of concentration.
1.
An ideal solution consisting of two components A and B (such as benzene and toluene) is one in what 1) the intermolecular attractions A, …. A, B, ….. B and A …. B are equal 2) H mix = 0, Vmix = 0 3) both of the above conditions are followed 4) none of the above conditions is followed
2.
VIII.
There is deviation from ideal behaviour if mixture contains: 1) n-hexane and n-heptane
2) chlorobenzene and bromobenzene
3) o-xylene and p-xylene
4) acetone and chloroform
Answer the questions (given below) which are based on the following diagram.
Vapour pressure diagram for real solutions of two liquids A and B that exhibit a negative deviation from Raoult’s law. The vapour pressure of both A and B are less than predicted by Raoult’s law. The dashed lines represent the plots for ideal solutions 1.
Solution containing components A and B shows this type of deviation from ideal behaviour when
1)
Attraction A … B
Hmix
larger than average of A .. A, B… B
+ve
Vmix +ve
b.p. larger than expected
attraction 2)
as in (a)
- ve
- ve
as in (a)
3)
smaller than average of A … A, B … B
+ve
+ve
smaller than expected
24
attraction 4) 2.
IX.
as in (c)
+ve
+ve
as in (c)
This type of deviation is also expected in the following mixture 1) ethanol and cyclohexane
2) ethyl bromide and ethyl chloride
3) benzonitrile and ethyl cyanide
4) diethyl ether and chloroform
Answer the questions (given below) which are based on the following diagram. Vapour pressure diagram for real solution of two liquids A and B that exhibit a positive deviation from Raoult’s law. The vapour pressure of both A and B are greater than predicted by Raoult’s law. The dashed lines represented the plots for ideal solutions.
1.
Consider some facts about the above phase diagram (A) This is observed when A … B attractions are greater than average of A … A and B … B attraction (B) AH mix = +ve, Vmix +ve (C) Boiling point is smaller than expected such that vaporization is increased (D) It forms azeotropic mixture Select correct facts : 1) A, B, C
2.
2) B, C, D
3) A, C, D
4) A, B, C, D
Total vapour pressure of mixture of 1 mol. of volatile component A p 0 A = 100 mm Hg and 3 mol. volatile
component B p 0 B = 60 mm Hg is 75mm. For such case 1) there is positive deviation from Raoult’s law 2) boiling point has been lowered 3) force of attraction between A and B is smaller than that between A and A or between B and B 4) all the above statements are correct X.
Read the following sentence and answer the question at the end of it. In case of positive and negative deviations shown by mixture of two solvents the boiling point composition curves have minima or maxima.
1.
Select correct statement(s) about this mixture of solvents
25
1) Separation of such mixture into their components can’t be obtained by simple or fractional distillation 2) Mixture is called azeotropic mixture 3) Mixture boils at a constant temperature and distills over without undergoing any change in the composition 4) Ethanol-water system shows positive deviation.
XI.
Read the following sentence and answer the questions at the end of it.
Benzoic acid dimerises in benzene but ionizes in aqueous solution
1.
2.
Equimolal solutions of (A) benzoic acid in benzene and (B) in aqueous solution are taken. Thus 1) van’t Hoff factor of (A) > (B)
2) van’t Hoff factor of (A) < (B)
3) van’t Hoff factor of (A) = (B)
4) dimmer formation or ionisation is not possible
In the following equilibrium
2NO 2 N 2O 4 (g) NO2 is 50% of the total volume. Hence, degree of dissociation (x) and van’t Hoff factor (i) respectively are 1) 0.5, 1.5 3.
2) 0.25, 1.25
4) 0.66, 1.66
Which has maximum freezing point? 1) 6g urea solution in 100g H2O 3) 6g sodium chloride in 100g H2O
4.
3) 0.33, 1.33
2) 6g acetic acid solution in 100g H2O 4) all have equal freezing point
Aluminium phosphate is 100% ionized in 0.01 mol. aqueous solution. Hence Tb K b is 1) 0.01
2) 0.015
3) 0.0175
4) 0.02
