CBSE Previous Year Questions

Chapter: SOLUTION (C) 114 g mol-1 (D) 3·42 g mol-1

CBSE 2024 10. Assertion (A): When NaCl is added in water, elevation in boiling
1. Van’t Hoff factor for Na2SO4.10H2O solution, assuming complete point is observed.
ionization is Reason (R): Elevation in boiling point is a colligative property.
(A) 1 (B) 3 (C) 13 (D) 2 11. Assertion (A): When NaCl is added to water a depression in freezing
2. For an electrolyte undergoing association in a solvent, the van’t point is observed.
Hofffactor: Reason (R): NaCl undergoes dissociation in water.
(A) is always greater than one (B) has negative value 12. Assertion (A): ∆mixH for an ideal solution is not equal to zero.
(C) has zero value (D) is always less than one Reason (R): A– B interactions in an ideal solution are same
3. Phenol dimerises in having van’t Hoff factor 0.54. Its degree of asbetween A– A and B – B interactions.
association is 13. Assertion (A): Addition of ethylene glycol to water lowers its
(A) 0·54 (B) 0·46 (C) 0·92 (D) 0·27 freezing point.
4. The system that forms maximum boiling azeotrope is: Reason (R): Ethylene glycol is insoluble in water due to lack of
(A) CS2 and acetone (B) Benzene and toluene itsability to form hydrogen bonds with water molecules.
(C) Ethanol and acetone (D) Chloroform and acetone 14. Assertion (A):∆mixH and ∆mixV are zero for non-ideal solutions.
5. An azeotropic solution of two liquids has boiling point lower than Reason (R): Solute-solvent interactions are not same as puresolute-
eitherof them when it : solute and pure solvent-solvent interactions innon-ideal
(A) is saturated solutions.
(B) shows positive deviation from Raoult’s Law 15. (a) Define molal depression constant. How is it related to enthalpy of
(C) shows negative deviation from Raoult’s Law fusion?
(D) shows no deviation from Raoult’s Law OR
6. An azeotropic solution of two liquids has boiling point higher than (b) What type of deviation is shown by ethanol and acetone mixture?
either of them when it: Give reason. What type of azeotropic mixture is formed by that
(A) is saturated eviation?
(B) shows positive deviation from Raoult’s Law 16. A solution is prepared by dissolving 5 g of a non-volatile solute in
(C) shows negative deviation from Raoult’s Law 200 g of water. It has a vapour pressure of 31·84 mm Hg at 300 K.
(D) shows no deviation from Raoult’s Law Calculate the molar mass of the solute.
7. The relative lowering of vapour pressure of an aqueous solution (Vapour pressure of pure water at 300 K = 32 mm Hg)
containing non-volatile solute is 0·0225. The mole fraction of the 17. A 6% solution of glucose (molar mass = 180 g mol -1) is isotonic with
non-volatile solute is: 2. 5% solution of an unknown organic substance. Calculate the
(A) 0·80 (B) 0·725 (C) 0·15 (D) 0·0225 molecular weight of the unknown organic substance.
8. On mixing 10 mL of acetone with 50 mL of chloroform, the total 18. 18g of a non-volatole solute is dissolved in 200g of H2O freezes at
volume of the solution will be: 272.07 K. Calculate the molecular mass of solute.
(A) < 60 mL (B) > 60 mL (C) = 60 mL (D) = 100 mL (Kf for water = 1.86 K kg mol-1)
9. A 1% solution of solute ‘X’ is isotonic with a 6% solution of sucrose 19. The vapour pressure of a solvent at 283 K is 100 mm Hg. Calculate
(molar mass = 342 g mol-1). The molar mass of solute ‘X’ is the vapour pressure of a dilute solution containing 1 mole of a strong
(A) 34·2 g mol-1 (B) 57 g mol-1
 electrolyte AB in 50 moles of the solvent at 283 K (assuming 22. (a) (i) Ishan’s automobile radiator is filled with 1.0 kg of water. How
complete dissociation of solute AB). many grams of ethylene glycol (Molar mass = 62 g mol-1) must
20. (a) (i) At the same temperature, CO2 gas is more soluble in water than Ishan add to get the freezing point of the solution lowered to –
O2 gas. Which one of them will have higher value of KH and why? 2.8 ºC. Kf for water is 1.86 K kg mol-1.
(ii) How does the size of blood cells change when placed in (ii) What type of deviation from Raoult’s law is shown by ethanol
anaqueous solution containing more than 0·9% and acetone mixture? Give reason.
(mass/volume)sodium chloride? OR
(iii) 1 molal aqueous solution of an electrolyte A2B3 is (b) (i) Boiling point of water at 750 mm Hg pressure is 99.68 ºC. How
60%ionized.Calculatethe boiling point of the solution. much sucrose (Molar mass = 342 g mol-1) is to be added to 500 g
1+1+3=5 of water such that it boils at 100 ºC? (Kb for water = 0.52 K kg
(Given: Kb for H2O = 0·52 K kg mol 1) mol-1)
OR (ii) State Henry’s law and write it’s any one application.
(b) (i) The vapour pressures of A and B at 25ºC are 75 mm Hg and25 CBSE 2023
mmHg, respectively. If A and B are mixed such that themole 1. The colligative property used for the determination of molar mass of
fraction of A in the mixture is 0·4, then calculate themole polymers and proteins is:
fraction of B in vapour phase. (a) Osmotic pressure (b) Depression in freezing point
(ii) Define colligative property. Which colligative property (c) Relative lowering in vapour pressure (d) Elevation is boiling point
ispreferred for the molar mass determination 2. Low concentration of oxygen in the blood and tissues of people living
ofmacromolecules? at high altitude is due to:
(iii) Why are equimolar solutions of sodium chloride and (a) high atmospheric pressure
glucosenotisotonic? (b) low temperature
21. (a) (i) Define reverse osmosis. (c) low atmospheric pressure
(ii) Why are aquatic species more comfortable in cold water in (d) both low temperature and high atmospheric pressure
comparison to warm water? 3. On dissolving ammonium chloride in water at room temperature, the
(iii) A solution containing 2 g of glucose (M = 180 g mol-1) in 100 solution feels cool to touch. Under which of the following conditions
g of water is prepared at 303 K. If the vapour pressure of pure does salt dissolve faster?
water at 303 K is 32.8 mm Hg, what would be the vapour (a) Powdered salt in cold water (b) Powdered salt in hot water
pressure of the solution? (c) Salt crystals in cold water (d) Salt crystals in hot water
OR 4. Value of Henry’s constant KH:
(b) (i) Predict whether Van’t Hoff factor will be less or greater than (a) increases with decrease in temperature.
one, when Ethanoic acid is dissolved in benzene. (b) decreases with increase in temperature.
(ii) Define ideal solution. (c) increases with increase in temperature.
(iv) Calculatethe mass of CaCl2 (molar mass = 111 g mol-1) to (d) remains constant.
be dissolved in 500 g of water to lower its freezing point 5. An azeotropic mixture of two liquids will have a boiling point lower
by 2K, assuming that CaCl2 undergoes complete than either of the two liquids when it
dissociation. (a) shows a negative deviation from Raoult’s law
(Kf for water = 1.86 K kg mol-1) (b) forms an ideal solution
(c) shows a positive deviation from Raoult’s law
 (d) is saturated (ii) A non-volatile solute ‘X’ (molar mass = 50 g mol–1)
6. Solubility of gas in liquid decreases with increase in whendissolved in78g of benzene reduced its vapour pressure to
(a) Pressure (b) Temperature 90%.Calculate the mass of X dissolved in the solution.
(c) Volume (d) Number of solute molecules (iii) Calculate the boiling point elevation for a solution prepared
7. A compound undergoes complete tetramerization in a given organic byadding10g of MgCl2 to 200g of water assuming MgCl2
solent. The Van’t Hoff factor ‘i’ is iscompletely dissociated.
(a) 4.0 (b) 0.25 (c) 0.125 (d) 2. 0 (Kb for Water = 0.512 K kg mol–1, Molar mass MgCl2 = 95g
–1
8. 1 mole of liquid A and 2 moles of liquid B make a solution having a mol )
total 16. (i) Why is the value of Van’t Hoff factor for ethanoic acid inbenzene
vapour pressure 40 torr. The vapour pressure of pure A and pure B are closeto 0.5? 1+2+2=5
45 (ii) Determine the osmotic pressure of a solution prepared
torr and 30 torr respectively. The above solution bydissolving2.32 ×10–2g of K2SO4 in 2L of solution at
(a) is an ideal solution. 25OC,assuming that K2SO4 is completely dissociated.
(b) shows positive deviation. (R = 0.082 L atm K–1 mol–1, Molar mass K2SO4 = 174g mol–1)
(c) shows negative deviation. (iii) When 25.6g of Sulphur was dissolved in 1000g of benzene,
(d) is a maximum boiling azeotrope. thefreezing point lowered by 0.512 K. Calculate the formula
9. If molality of a dilute solution is doubled, the value of the molal ofSulphur (Sx).
elevationconstant (Kb) will be (Kf for benzene = 5.12 K kg mol–1, Atomic mass of Sulphur =
(a) halved (b) doubled (c) tripled (d) unchanged 32gmol–1)
10. What is Henry’s Law? Give one application of it. 17. (a) Find the value of factor for acetic acid in benzene as perthe given
11. Assertion (A): Osmotic pressure is a colligative property. equation:2CH3COOH ═ (CH3COOH)2, assuming its complete
Reason (R): Osmotic pressure is proportional to the molality. association.
12. (a) Differentiate between Ideal solution and Non-ideal solution. (b) Osmotic pressure of a solution containing 3·5 g of dissolved
(b) 30 g of urea is dissolved in 846 g of water. Calculate the vapour proteinin 0·05 L of a solution is 0·035 atm at 310 K. Calculate the
pressure of water for this solution if vapour pressure of pure water molarmass of the protein. (R = 0·0821 L atm K-1 mol-1)
at 298 K is 23 8 mm Hg. case study
13. The vapour pressure of pure liquid X and pure liquid Y at 25 0C are Raoult’s for volatile liquids states that the partial vapour pressure ofeach
120 mm Hg and 160 mm Hg respectively. If equal moles of X and Y component in the solution is directly proportional to its mole
are mixed to form an ideal solution, calculate the vapour pressure of fraction,whereas for a non-volatile solute, it states that the vapour pressure
the solution. of asolution of a non-volatile solute is equal to the vapour pressure of the
14. When 19.5 g of F – CH2 – COOH (Molar mass = 78 g mol–1), is puresolvent at that temperature multiplied by its mole fraction. Two
dissolved in500 g of water, the depression in freezing point is liquids Aand B are mixed with each other to form a solution, the vapour
observed to be 1oC. phaseconsists of bothcomponents of the solution. Once the components in
Calculate the degree of dissociation of F – CH2 – COOH.
thesolution have reached equilibrium, the total vapour pressure of
[Given: Kffor water = 1.86 K kg mol–1]
thesolution can be determined by combining Raoult’s law with Dalton’s
15. (i) Why is boiling point of 1M NaCl solution more than that of
law of partial pressures. If a non-volatile solute B is dissolved into a
1Mglucose solution? 1 + 2 + 2 = 5
solvent A toform a solution, the vapour pressure of the solution will be
lower thanthat of the pure solvent. The solutions which obey Raoult’s law
over theentire range of concentration are ideal solutions, whereas the 4. Calculate the mass of ascorbic acid (Molar mass = 176 g mol–1) to be
solutions forwhich vapour pressure is either higher or lower than that dissolved in 75 g of acetic acid, to lower its freezing point by 1·5O C.
predicted byRaoult’s law arecalled non-ideal solutions. Non-ideal (Kf = 3·9 K kg mol–1)
solutions areidentified by determining the strength of the intermolecular 5. Predict the state of the solute in the solution in the following
forcesbetween the different molecules in that particular solution. They situations:
caneither show positive or negative deviation from Raoult’s law (a) When ‘i’ is found to be more than one.
dependingon whether the A – B and B – B interactions in solution are (b) When ‘i’ is found to be less than one.
stronger or weaker thanand interactions. 6. An antifreeze solution is prepared by dissolving 31 g of ethylene
glycol
Answer the following questions: (Molar mass = 62 g mol–1) in 600 g of water. Calculate the freezing
(a) 20 mL of a liquid A was mixed with 20 mL of liquid B. The volumeof pointof the solution. (Kf for water = 1·86 K kg mol–1)
resulting solution was found to be less than 40 mL. What do 7. (a) A solution contains 5·85 g NaCl (Molar mass = 58·5 g mol–1) per
youconclude from the above data? litre of solution. It has an osmotic pressure of 4·75 atm at 27ºC.
(b) Which of the following show positive deviation fromCarbon Calculate the degree of dissociation of NaCl in this solution.
disulphide and Acetone; Phenol and Aniline; Ethanol andAcetone (Given: R = 0·082 L atm K–1 mol–1)
(c) The vapour pressure of a solution of glucose in water is 750 mm Hgat (b) State Henry’s law. Why is air diluted with helium in the tanksused
100 ºC. Calculate the mole fraction of solute. by scuba divers?
(Vapour pressure of water at 373 K = 760 mm Hg) OR
OR (a) When 19·5 g of F – CH2 – COOH (Molar mass = 78 g mol–1)
(c) The boiling point of solution increases when 1 mol of NaCl is addedto isdissolved in 500 g of water, the depression in freezingpoint is
1 litre of water while addition of 1 mol of methanol to one litre observed to be 1ºC. Calculate the degree of dissociation ofF – CH2 –
ofwater decreases its boiling point. Explain the above observations. COOH.
CBSE 2020 [Given: Kf for water = 1·86 K kg mol–1]
1. 50 mL of an aqueous solution of glucose C6H12O6 (Molar mass: 180 (b) Give reasons:
g/mol) contains 6·02 × 1022 molecules. The concentration of the (i) 0·1 M KCl has higher boiling point than 0·1 M Glucose.
solution will be (ii) Meat is preserved for a longer time by salting.
(A) 0·1 M (B) 0·2 M (C) 1·0 M (D) 2·0 M CBSE 2019
2. Identify which liquid will have a higher vapour pressure at 90ºC if the 1. State Raoult’s law for a solution containing volatile components.
boiling points of two liquids A and B are 140ºC and 180ºC, Write two characteristics of the solution which obeys Raoult’s law at
respectively. all concentrations.
3. For a 5% solution of urea (Molar mass = 60 g/mol), calculate the 2. A 4% solution(w/w) of sucrose (M = 342 g mol–1) in water has a
freezing point of 271.15 K. Calculate the freezing point of 5% glucose
osmotic pressure at 300 K. [R = 0·0821 L atm K–1 mol–1] 2
(M = 180 g mol–1) in water. (Given : Freezing point of pure water =
OR 273.15 K)
Visha took two aqueous solutions — one containing 7·5 g of urea 3. Give reasons:
(Molar mass = 60 g/mol) and the other containing 42·75 g of (a) Cooking is faster in pressure cooker than in cooking pan.
substance Z in 100 g of water, respectively. It was observed that both (b) Red Blood Cells (RBC) shrink when placed in saline water
the solutions froze at the same temperature. Calculate the molar mass butswell in distilled water.
of Z.
4. A solution containing 1·9 g per 100 mL of KCl (M = 74·5 g mol–1) itto be completely dissociated. (Atomic masses K = 39 u, S = 32
isisotonic with a solution containing 3 g per 100 mL of urea(M = 60 g u,O = 16 u)
mol–1). Calculate the degree of dissociation of KCl solution.Assume 13. (a) Write two characteristics of non-ideal solution.
that both the solutions have same temperature. (b) 2 g of benzoic (C6H5COOH) dissolved in 25 g of benzene shows
5. Give reasons: adepression in freezing point equal to 1·62 K. Molal
(a) A decrease in temperature is observed on mixing ethanol depressionconstant for benzene is 4·9 K kg mol–1. What is the
andacetone. percentageassociation of acid if it forms dimer in solution?
(b) Potassium chloride solution freezes at a lower temperature than 14. (a) A 5% solution (by mass) of cane sugar in water has a freezing
water. point of 271 K. Calculate the freezing point of 5% solution (by
6. Give reasons: mass) of glucose in water. The freezing point of pure water is
(a) An increase in temperature is observed on mixing chloroform 273·15 K.
andacetone. (b) Why is osmotic pressure of 1 M KCl higher than 1 M urea
(b) Aquatic animals are more comfortable in cold water than in solution?
warmwater. (c) What type of liquids form ideal solutions?
7. (a) Out of 0·1 molal aqueous solution of glucose and 0·1 molal 15. (a) 1·0 g of a non-electrolyte solute dissolved in 50 g of benzene
aqueoussolution of KCl, which one will have higher boiling point lowered the freezing point of benzene by 0·40 K. The freezing
and why ? point depression constant of benzene is 5·12 K kg mol–1. Find the
(b) Predict whether van’t Hoff factor, (i) is less than one or greaterthan molar mass of the solute.
one in the following: (i) CH3COOH dissolved in water (b) What is the significance of Henry’s law constant, KH?
(ii) CH3COOH dissolved in benzene (c) What leads to anoxia?
8. A solution 0·1 M of Na2SO4 is dissolved to the extent of 95%. What CBSE 2018
would be its osmotic pressure at 27ºC? (R = 0·0821 L atm K–1 mol–1) 1. Calculate the freezing point of a solution containing 60 g of glucose
9. Give reasons for the following: (Molar mass = 180 g mol–1) in 250 g of water. (Kf of water = 1·86 K
(a) Aquatic species are more comfortable in cold water than kg mol–1)
warmwater. 2. Give reasons for the following :
(b) At higher altitudes people suffer from anoxia resulting in (a) Measurement of osmotic pressure method is preferred for the
inabilityto think. determination of molar masses of macromolecules such as
10. What type of azeotropic mixture will be formed by a solution of proteins and polymers.
acetone and chloroform? Justify on the basis of strength of (b) Aquatic animals are more comfortable in cold water than in
intermolecularinteractions that develop in the solution. warmwater.
11. At 300 K, 30 g of glucose present in a litre of its solution has an (c) Elevation of boiling point of 1 M KCl solution is nearly double than
osmotic pressure of 4·98 bar. If the osmotic pressure of a glucose that of 1 M sugar solution.
solution is 1·52 bar at the same temperature, what would be its CBSE 2017
concentration? 1. (a) Explain why on addition of 1 mol glucose to 1 litre water the
12. (a) Draw the graph between vapour pressure and temperature and boiling point of water increases.
explain the elevation in boiling point of a solvent in solution. (b) Henry’s law constant for CO2 in water is 1.67 ×108 Pa at 298 K.
(b) Determine the osmotic pressure of a solution prepared Calculatethe number of moles of CO2 in 500 ml of soda water
bydissolving 25mg of K2SO4 in 2 litres of water at 25ºC assuming when packed under2.53 ×105 Pa at the same temperature.
 OR
(a) Define the following terms:
(i) Ideal solution (ii) Osmotic pressure.
(b) Calculate the boiling point elevation for a solution prepared by
adding10 g CaCl2 to 200 g of water, assuming that CaCl2 is
completely dissociated.(Kb for water = 0.512 K kgmol–1; Molar
mass of CaCl2 = 111 g mol–1)
CBSE 2016
1. (a) Gas (A) more soluble in water than gas (B) at the same
temperature. Which one of the two gases will have higher value
of KH (Henry’s law constant) and why?
2. In non-ideal solution, what type of deviation shows the formation
of maximum boiling azeotropes?
3. Calculate the boiling point of solution when 4 g of MgSO4 (M =
120 gmol-1) was dissolved in 100 g of water, assuming MgSO4
undergoes complete ionization. ( Kbfor water = 0.52 K Kg mol-1)
4. Write two differences between a solution showing positive
deviation and a solution showing negative deviation from
Raoult’s law.