Lakshya JEE AIR 2025

Solution [LAKSHYA]

Single Correct Type Questions

1. The only incorrect statement regarding Henry's law
for a gas dissolving in water is
(A) The value of KH (Henry's constant) is greater
for O2 than H2 at same temperature.
(B) The value of KH increases with increase in
temperature.
(c) Henry's law is not applicable for HCl(g). (A) Composition of the still (residue) will
(d) Henry's law is applicable when the solubility approach pure liquid B
of gas is very low. (B) Composition of the distillate will approach
pure A
2. A beaker (A) contains 20 g sugar in 100 g water. (C) Composition of distillate and residue will
Another beaker (B) contains 10 g of sugar in 100 g approach pure B and A respectively
water. Both the beakers are placed under a bell jar (D) Neither of the component can be obtained in
and allowed to stand until equilibrium is reached. pure state
How much water will be transferred from one
beaker to the other? Neglect the mass of water 5. Equal weight of a solute are dissolved in equal
vapour present at equilibrium. weight of two solvents A and B and formed very
(A) 0 dilute solution. The relative lowering of vapour
(B) 33.33 g water will transfer from beaker-A to pressure for the solution B has twice the relative
beaker-B. lowering of vapour pressure for the solution A. If
(C) 33.33 g water will transfer from beaker-B to MA and MB are the molecular weights of solvents
beaker-A. A and B respectively, then:
(D) 50.00 g water will transfer from beaker-B to (A) MA = MB (B) MB = 2 × MA
beaker-A. (C) MA = 4MB (D) MA = 2MB

3. The immiscible liquid system containing aniline- 6. Dry air was passed successively through a solution
water boils at 98° C under a pressure of 760 mm. of 5 g of a solute in 80 g of water and then through
At this temperature, the vapour pressure of water is pure water. The loss in mass of solution was 2.5 g
700 mm. If aniline is distilled in steam at 98°C, and that of pure solvent was 0.04 g. What is the
then what percent of total weight of the distillate molecular mass of the solute?
will be aniline? (A) 70.3 (B) 71.43
(A) 7.89% (C) 14.28 (D) 14.06
(B) 8.57%
(C) 30.7% 7. Insulin is dissolved in a suitable solvent and the
(D) 44.3% osmotic pressure (π) of solutions of various
concentrations C(g/cm3) is measured at 20°C. The
4. Boiling point composition diagram of the liquid- slope of a plot of π against C is found to be 4.65 ×
vapour equilibrium for A and B is shown in the 10–3. The molecular weight of the insulin (g/mol) is
figure. If a binary liquid mixture of A and B is (A) 3 × 105
distilled fractionally, which of the following would (B) 9 × 105
be correct observation? (C) 4.5 × 105
(D) 5.16 × 106

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 Tb (A) blue colour formation in the side X.
8. Ratio of of 10 g AB2 and 14 g A2B per 100 g
Kb (B) blue colour formation in the side Y.
(C) blue colour formation in both sides of X and Y.
of solvent in their respective, solution (AB2 and
(D) no blue colour formation.
A2B both are non-electrolytes) is 1 mol/kg in both
cases. Hence, atomic wt. of A and B are 12. Which of the following represents correct
respectively difference when non-volatile solute is present in an
(A) 100, 40 (B) 60, 20 ideal solution?
(C) 20,60 (D) None of these

9. A non-volatile solute 'X' completely dimerizes in (I)

water, if the temperature is below –3.72°C and the
solute completely dissociates as X → Y + Z, if the
temperature is above 100.26°C. In between these
(II)
two temperatures (including both temperatures),
the solute is neither dissociated nor associated. One
mole of 'X' is dissolved in 1.0 kg water (Kb = 0.52
K-kg/mol, Kf = 1.86 K-kg/mol). Identify the
incorrect information related with the solution. (III)
(A) The freezing point of solution is –1.86°C.
(B) The boiling point of solution is 101.04°C. (A) I, II, III (B) I, III only
(C) When the solution is cooled to –7.44°C, 75% (C) II, III only (D) I, II only
of water present initially will separate as ice.
13. The vapour pressure curves of the same solute in
(D) When the solution is heated to 102.08°C, 50%
the same solvent are shown. The curves are parallel
of water present initially will escape out as
to each other and do not intersect. The
vapour. concentrations of solutions are in order of:

10. A liquid mixture of 'A' and 'B' (assume ideal

solution) is placed in a cylinder and piston
arrangement. The piston is slowly pulled out
isothermally so that the volume of liquid decreases
and that of the vapour increases. At the instant
when the quantity of the liquid still remaining is (A) I < II < III (B) I = II = III
negligibly small, the mole fraction of ' A ' in the (C) I > II > III (D) I > III > II
vapour is 0.4. If PAo = 0.4 atm and PBo = 1.2 atm at
14. A liquid mixture having composition corresponding
this temperature, then the total pressure at which to point Z in the figure shown is subjected to
the liquid has almost evaporated is distillation at constant pressure. Which of the
(A) 0.667 atm (B) 1.5 atm following statement is correct about the process?
(C) 0.8 atm (D) 0.545 atm

11. FeCl3 solution (side X) on reaction with

K4[Fe(CN)6] (side Y) in aqueous solution gives
blue colour. These are separated by a
semipermeable membrane as shown. Due to (A) The composition of distillate differs from the
osmosis, there is mixture
(B) The boiling point keeps on changing
(C) The mixture has highest vapour pressure than
for any other composition
(D) Composition of an azeotrope alters on
changing the external pressure

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15. The amino acid alanine has two isomers, such as α- 19. The total vapour pressure of a binary solution is
alanine and β-alanine. When equal masses of these given by
two compounds are dissolved in equal mass of a P = (100 XA + 260 XB) mm Hg
solvent, the solution of α-alanine freezes at where, XA and XB are the mole fractions of
relatively lower temperature. Which forms α- components A and B. This indicates that the:
alanine or β-alanine, has the larger equilibrium (A) vapour pressure of solution is less than the
constant for ionization? pure B component
(A) α-alanine (B) β-alanine (B) vapour pressure of solution is more than that
(C) Same for both (D) Unpredictable of pure A component
(C) vapour pressure of pure A is 100 mm Hg and
One or more than one correct type questions: that of pure B is 260 mm Hg
16. In which of the following liquid pairs, there is (D) the vapour pressure of pure A and B are 260
contraction in volume on mixing? mm Hg and 100 mm Hg respectively
(A) C6H14 + C6H6 (B) H2O + HCl
(C) H2O + HNO3 (D) H2O + C2H5OH 20. Which of the following statement(s) is/are correct
about acetone and trichloromethane mixture?
17. 2 litre of 1 molar solution of a complex salt (A) mixtures of acetone and trichloromethane
CrCl3⋅6H2O (molar mass 266.5 g mol–1) shows an shows positive deviation from Raoult's law
osmotic pressure of 98.52 atm. The solution is now (B) the forces of attraction acting between
treated with 1 litre of 6 M AgNO3, which of the molecules of acetone and trichloromethane in
following is/are correct? a mixture are greater than those acting
(A) Mass of AgCl precipitated is 861 g between the molecules in pure acetone
(B) The clear solution will show an osmotic (C) pure acetone can be obtained by the careful
pressure = 98.52 atm fractional distillation of any mixture of
(C) The clear solution will show an osmotic acetone and trichloromethane
pressure = 65.68 atm (D) when acetone and trichloromethane are
(D) 2 mole of [Cr(H2O)6] (NO3)3 will be present in mixed, the enthalpy change is negative
solution
21. Consider following solutions:
18. Based on the given diagram, which of the (I) 1 M glucose (aq)
following statement(s) regarding the homogeneous (II) 1 M sodium chloride (aq)
solutions of two volatile liquids is are correct? (III) 1 M acetic acid in benzene
(IV) 1 M ammonium phosphate (aq)
(A) all are isotonic solutions
(B) III is hypotonic of I, II, IV
(C) I, II, IV are hypertonic of III
(D) IV is hypertonic of I, II, III

(A) Plots AD and BC show that Raoult's law is 22. Consider following solutions:
obeyed for the solution in which B is a solvent 0.1 m C6H5NH3+Cl− ; 0.1 m KCl; 0.1m Glucose;
and A is the solute and as well as for that in
0.1 m Na2C2O4⋅10 H2O
which A is solvent and B is solute.
(A) the solution with highest boiling point is 0.1 m
(B) Plot CD shows that Dalton's law of partial
Na2C2O4⋅10H2O
pressures is obeyed by the binary solution of
(B) the solution with highest freezing point is 0.1
components A and B.
m glucose
(C) EF + EG = EH; and AC and BD correspond to
(C) 0.1 m C6H5NH3Cl and 0.1 m NaCl will have
the vapour pressures of the pure solvents A
the same osmotic pressure
and B respectively.
(D) 0.1 m glucose solution will have the lowest
(D) Solution shows positive deviation from ideal
osmotic pressure
nature
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23. Two miscible liquids A and B having vapour (A) NaCl, i = 2 + α
pressure in pure state as PAo and PBo are mixed in (B) Ca(NO3)2, i = 1 + 2α
mole fraction χA and χB to get a mixture having total (C) K4[Fe(CN)6], i = 1 + 4α
(D) (NH4)3PO4, i = 3 + α
vapour pressure of mixture PM. Which of the
following relation(s) are correct?
28. Composition of an azeotrope
P − PBo A(l ) PM
(A) A = Mo (B) = (A) Is indepndent of external pressure because it is
PA − PBo  'A(V) PAo a compound
A(l ) (B) Alters on changing the external pressure as it
PM
(C) = (D) All of these is not a compound
 'A(V) PBo (C) Remains unchanged during distillation at a
constant external pressure
24. Which of the following relations is/are correct for (D) Fluctuates even at constant pressure
an aqueous dilute solution of K3PO4 if its degree of
dissociation is α ? 29. A mixture of two immiscible liquids A and B, having
P Molality 18  (1 + 3) vapour pressure in pure state obeys the following
(A)  =
P 1000 relationship if χA and χB are mole fractions of A and
P obs 18  (1 + 3) B in vapour phase over the solution
(B) = 
P RT 1000 (A) PA = PMA
P ( Tf )obs 18 PA W  Mw B
(C) = (B) 
= A
P Kf 1000 PB Mw A  WB
(D) Mw of K3PO4 = Mwobs × (1 + 3α) (C) If PA  PB then A  B
25. Which of the following statement(s) is (are) (D) If PA  PB , then nA > nB
incorrect?
(A) 0.1 M KCl solution will have the same 30. For a binary ideal liquid solution, the variation in
osmotic pressure as 0.1 M glucose solution total vapour pressure versus composition of
(B) 0.1 M KCl solution will have the same boiling solution is given by which of the following curves?
point as 0.1M urea solution
(C) 0.1 m glucose and 0.1 m urea are isotonic
(D) 0.1 m MgCl2 solution will have less relative (A) (B)
lowering of vapour pressure than 0.1 m NaCl

26. Following is a graph plotted between the vapour

pressure of two volatile liquids against their
respective mole fractions.
(C) (D)

31. This type of diagram is true for

Which of the following statements is/are correct?

(A) When χA = 1 and χB = 0, then P = PAo .
(B) When χB = 1 and χA = 0, then P = PB .
(C) When χA = 1 and χB = 0, then P < PB .
(D) When χB = 1 and χA = 0, then P > PA . (A) CH3Cl + CH3Br
(B) C6H6 + C6H5CH3
27. For a given value of degree of dissociation, which (C) CH3COCH3 + CHCl3
of the following have correct Van't Hoff factor? (D) HNO3 + H2O

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32. We have three aqueous solutions of NaCl labelled (A) It is temperature-composition diagram for a
as 'A', 'B' and 'C' with concentrations 0.1 M, 0.01 high-boiling azeotrope
M and 0.001 M, respectively. For such solutions (B) As fractional distillation proceeds the
(A) iA < iB < iC (B) iA > iB > iC composition of the remaining liquid moves
(C) πA > πB > πC (D) πA < πB < πC towards a4
(C) Azeotrope is not separable into individual
components
33. Consider the Fig. and mark the incorrect options.
(D) If vapour in equilibrium with liquid has the
same composition, mixture evaporates with
unchanged composition

36. In which of the following case(s), van't Hoff factor

(i) remains unchanged?
(A) PtCl4 reacts with KCl
(B) Aq. ZnCl2 reacts with Aq. NH3 (excess)
(C) Aq. FeCl3 reacts with Aq. K4[Fe(CN)6]
(D) HgCl2 reacts with excess of KI
(A) water will move from side (A) to side (B) if a
Paragraph type questions:
pressure lower than osmotic pressure is
PASSAGE-I
applied on piston (B) The two liquids 'A' and 'B' have the same molecular
(B) water will move from side (B) to side (A) if a mass and form ideal solution. The solution has the
pressure greater than osmotic pressure is vapour pressure 700 mm at 80°C. The above
applied on piston (B) solution is distilled without reflux. Three-fourth of
(C) water will move from side (B) to side (A) if a the solution is collected as condensate The mole
pressure equal to osmotic pressure is applied fraction of 'A' in the condensate is 0.75 and that in
on piston (B) the residue is 0.3. The vapour pressure of the
(D) water will move from side (A) to side (B) if residue at 80°C is 600 mm.
pressure equal to osmotic pressure is applied 37. The mass ratio of 'B' and 'A' in the initial solution
at equilibrium at 80°C was
on piston (A)
(A) 1 : 1 (B) 29 : 51
(C) 51 : 80 (D) 29 : 80
34. You have been provided with 10.00% by mass
solution of ethanol in water. 38. The vapour pressure of pure liquid 'A' at 80°C is
At 15°C, density = 0.9831 g mL–1 (A) 807.4 mm (B) 511.1 mm
At 25°C, density = 0.9804 g mL–1 (C) 755.6 mm (D) 533.3 mm
Select the correct statement(s).
(A) Molarity at 15°C is larger than that at 25°C 39. The vapour pressure of pure liquid 'B' at 80°C is
(B) Molarity at 25°C is larger than that at 15°C (A) 807.4 mm (B) 511.1 mm
(C) Molality at both temperature are equal (C) 755.6 mm (D) 533.3 mm
(D) Molality at 25°C is larger than that at 15°C
PASSAGE-II
Liquids 'A' and 'B' forms an ideal solution. At T K,
35. Select the correct statements about given diagram
PAo = 0.4 bar and PBo = 0.6 bar. In a cylinder piston
arrangement, 2.0 moles of vapours of liquid 'A' and
3.0 moles of vapours of liquid 'B' are taken at T K
and 0.3 bar.

40. If the vapours are compressed slowly and

isothermally, then at what pressure, the first drop
of liquid will appear?
(A) 0.4 bar (B) 0.5 bar
(C) 0.52 bar (D) 0.6 bar

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41. If the initial volume of vapours was 10.0 dm3, then III 0.1 M urea R Solution with lowest
at what volume, the first drop of liquid will form? osmotic pressure
(A) 6.0 dm3 (B) 4.0 dm3 IV 0.1 M MgCl2 S Solution with lowest
(C) 10.0 dm3 (D) 1.0 dm3 freezing point
T Solution with highest
vapour pressure
42. What is the composition of last traces of vapours
I II III IV
remained?
(A) Q R Q,T P,Q,S
2
(A) YA = (B) P,Q,S Q R, T Q
5
(C) Q R P,Q,S Q
1 (D) R, T Q Q P,Q,S
(B) YA =
2
9 46. Match the following
(C) YA =
13 List-I (Solute) List-II
4 (Van’t Hoff factor, i)
(D) YA =
13 I AlCl3 if α = 0.8 P i = 3.4
II BaCl2 if α = 0.9 Q i = 2.8
43. Which of the following is the only incorrect III Na3PO4 if α = 0.9 R i = 3.8
IV K4[Fe(CN)6] if α = 0.7 S i = 3.7
information regarding the composition of the
T i = 2.6
system at 0.51 bar pressure?
I II III IV
(A) XA = 0.45
(A) P Q S R
6
(B) YA = (B) R S Q P
17
(C) P T S R
12 (D) S P R Q
(C) nA(liquid) =
11
12 47. Match list-I with list-I
(D) nA (vapour) =
11 pA = partial pressure of component A in liquid
mixture, PAo = vapour pressure of pure A, χA =
Matrix Match type questions:
mole fraction of A in liquid mixture
44. Match the following if the molecular masses of X,
List-I List-II
Y and Z are same.
I C2H5OH + H2O P Azeotropic mixture
List- I (Solvent and List-II (Molal
II C2H5Br + Q Obeys Raoult's law
its boiling point) elevation constant,
C2H5I
Kb)
III o
pA = χA PA R Non-ideal solution
I X (100°C) P 0.68
with positive
II Y (27°C) Q 0.53
deviation
III Z (253°C) R 0.98
IV H2O + H2SO4 S Non-ideal solution
IV W (182°C) S 0.79
with negative
I II III IV deviation
(A) P Q R S T Ideal solution
(B) S R Q P I II III IV
(C) Q R P S (A) P, S P, R Q,T P, R
(D) S Q R P (B) Q, T P, S P, R Q, T
(C) P, R Q, T Q,T P, S
45. Match the following (D) Q, T P, R Q, T Q, T
List-I List-II
I 0.1 M P Solution with highest
Al2(SO4)3 boiling point
II 0.1 M AlPO4 Q Van't Hoff factor is greater
than 1

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48. 52. The vapour pressure of a certain liquid is given by
Volatile Vapour pressure the equation:
Molar mass
component at 350 K 313.7
A 24 kPa 60 g mol–1 log10 P = 3.54595 + + 1.40655log10 T
T
B 12 kPa 40 g mol–1 where P is the vapour pressure in mm and T is
100 g of binary mixture of A and B contains 60% temperature in K. Determine the value of molar
of A. Mixture is subjected to the following latent heat of vaporisation in kcal at 80 K.
operation.
Distil
Original mixture I ⎯⎯⎯ → II containing vapours 53. When cells of the skeletal vacuole of a frog were
Condense
of A and B ⎯⎯⎯⎯→ III (liquid) ⎯⎯⎯→ IV Distil placed in a series of NaCl solutions of different
containing vapours of A and B concentrations at 6°C, it was observed
microscopically that they remained unchanged in
Match the content of List I with their values in List
x% NaCl solution, it shrinks in more concentrated
II and select the answer from the codes given
solutions and swells in more dilute solutions. Water
below.
freezes from the x% salt solution at – 0.40°C. If the
List-I List-II(Mole fraction of A)
osmotic pressure of the cell cytoplasm at 6°C is
I Mixture I P 0.25
II Mixture II Q 0.50
'y' × 0.0821 atm, then the value of 'y' is _____.
III Mixture III R 0.67 (Kf = 1.86 K mol–1 kg)
IV Mixture IV S 0.80
T 0. 43 54. Two solutions of non-volatile solutes A and B
I II III IV having molar mass ratio of A and B(MA/MB) as 1/3
(A) P Q Q S are prepared by dissolving 5% (mass/vol.) of each
(B) P R S Q in water. The ratio of freezing point depression,
(C) Q T R S ( Tf )A
comes out to be 3 : 1. If the two solutions
(D) S Q T P ( Tf )B
are mixed to prepare a new solution (S1) by mixing
Numerical value type questions in the ratio 2:3 by volume and another new solution
49. A quantity of 1.04 g of (CoCl3⋅6NH3) (molecular (S2) is obtained by mixing in the ratio 3:2, find out
weight = 267) was dissolved in 100 g of H2O. The ( Tf )s1
freezing point of the solution was –0.29°C. How . Assume density of solution A and B
many moles of solute particle exist in solution for ( Tf )s
2
each mole of solute introduced? The value of Kf for equal to one.
water = 1.86°C m–1.
55. A solution containing compound 'X' in water and a
50. Solutions A and B have osmotic pressures of 2.4 atm solution containing glucose in water were put in a
and 4.2 atm, respectively, at a certain temperature. closed system. By doing this, some water vapour
The osmotic pressure (in atm) of a solution prepared was removed from one solution and got condensed
by mixing the solutions in 2 : 1 volume ratio, in the other. It is found that when both the solutions
respectively, at the same temperature is ____. were at equilibrium vapour pressure, one solution
contains 10% (w/w) of 'X' and the other 5%(w/w)
51. 1 g of a mixture containing NaCl and CaCl2 is glucose. The molar mass (in g/mol ) of 'X' is____.
dissolved in water. Sodium oxalate on addition to
this solution completely converts CaCl2 to CaC2O4. 56. A certain mass of a substance when dissolved in
The CaC2O4 is filtered and dissolved in dil. H2SO4. 100 g C6H6 lowers the freezing point by 1.28°C.
The clear solution requires 22 mL of 0.1 M The same mass of solute dissolved in 100 g of
KMnO4. Calculate freezing point (in K) of an water lowers the freezing point by 1.40°C. If the
aqueous solution prepared by dissolving 5 g of substance has normal molar mass in benzene and is
same mixture containing CaCl2 and NaCl in 100 g completely dissociated in water, then into how
water. Kf of water is 1.86 K kg–1 mol–1. [Assume many ions does it dissociate in water?
complete dissociation of CaCl2 and NaCl, Freezing K f for H2O and C6H6 are 1.86 and 5.12 K mol–1 kg
point of water = 273 K] respectively.

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57. Variation of π/c vs c (c is concentration of solute in 59. At 20°C, the vapour pressure of 0.1 molal aqueous
g dm–3) is given. At 300 K, for a solute of molar solution of urea is 0.03 mm less than that of water
mass 308 g mol–1, OA = x ×10–y in scientific and the vapour pressure of 0.1 molal solution of
notation with x as single digit integer. What is KCl is 0.0594 mm less than that of water. The
value of x? apparent percentage dissociation of KCl in water at
(R = 0.0821 L atm mol–1 K–1) the given temperature is _____% (Neglect the
moles of solute particles in comparison to the
moles of water in both solutions.)

60. At 10°C, the osmotic pressure of urea solution is 500

mm. The solution is diluted and the temperature is
raised to 25°C, when the osmotic pressure is found to
be 105.3 mm. The extent of dilution (ratio of final to
58. How many grams of ethylene glycol should be initial volume of solution) is _____.
mixed in 795 g water to form an antifreeze solution
that will not start to freeze until the temperature
reaches –30°C? (Kf for water = 1.86)

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 ANSWER KEY
1. (A) 21. (B, C, D) 41. (A)
2. (C) 22. (A, B, C, D) 42. (D)
3. (C) 23. (A, B) 43. (D)
4. (C) 24. (A, C, D) 44. (A)
5. (B) 25. (A, B, D) 45. (B)
6. (A) 26. (A, B) 46. (A)
7. (D) 27. (B, C) 47. (C)
8. (B) 28. (B, C) 48. (C)
9. (C) 29. (A, B, D) 49. (4)
10. (A) 30. (A, D) 50. (3)
11. (D) 31. (A, B) 51. (270.23)
12. (A) 32. (A, C) 52. (1.67)
13. (A) 33. (A, C, D) 53. (60)
14. (D) 34. (A, C) 54. (0.81)
15. (A) 35. (A, B, C) 55. (380)
16. (B, C) 36. (B, D) 56. (3)
17. (A, C, D) 37. (B) 57. (8)
18. (A, B, C) 38. (A) 58. (795)
19. (A, B, C) 39. (B) 59. (98)
20. (B, D) 40. (B) 60. (5)

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