Solutions
2
21
ns
Solutions
What are isotonic solutions?
Q.2.
How is it that measurement of osmotic pressure is more widely used for determining molar masses
of macromolecules than the elevation in boiling point or depression in freezing point of their
solutions?
Q.3.
How does the molarity of a solution change with temperature?
Q.4.
When and why is molality preferred over molarity in handling solutions in chemistry?
Q.5.
Why is the vapour pressure of a solution of glucose in water lower than that of water?
Q.6.
Define mole fraction.
Q.7.
What is the similarity between Raoult’s law and Henry’s law?
Q.8.
Out of two 0.1 motal solutions of glucose and of potassium chloride, which one will have a higher
boiling point and why?
Q.9.
Write two characteristics of non-ideal solution.
Q.10.
What type of liquids form ideal solutions?
Q.11.
Under what condition do non-ideal solutions show negative deviations?
Q.12.
What are maximum boiling azeotropes? Give one example.
Q.13.
Define molal depression constant or cryoscopic constant.
Q.15.
Q.16.
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What do you understand by the term that Kf for water is 1.86 K kg mol-1?
What is an antifreeze?
What is de-icing agent? How does it work?
Why is osmotic pressure of 1 M KCl higher than 1 M urea solution?
M
Q.17.
O
S
Q.14.
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Q.1.
Q.18.
What is the van’t Hoff factor for a compound which undergo dimerisation in an organic solvent?
Q.19.
What would be the value of van’t Hoff factor for a dilute solution of K2SO4 in water?
Q.20.
Why is glycol and water mixture used in car radiators in cold countries?
Q.21.
Why are the aquatic species more comfortable in cold water in comparison to warm water?
Q.22.
The dissociation of ammonium chloride in water is an endothermic process but still it dissolves in
water readily. Why?
Q.23.
What will happen to freezing point of a potassium iodide aqueous solution when mercuric iodide is
added to solution?
Q.24.
Define the term osmotic pressure. Describe how the molecular mass of a substance can be determined
by a method based on measurement of osmotic pressure.
Q.25.
Give reasons:
(i) Cooking is faster in pressure cooker than in cooking plan.
(ii) Red Blood Cells (RBC) shrink when placed in saline water but swell in distilled water.
9818536667
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Q.26.
State Raoult’s law for the solution containing volatile components. What is the similarity between
Raoult’s law and Henry’s law?
Q.27.
State Henry’s law. Write its one application. What is the effect of temperature on solubility of gases
in liquid?
Q.28.
State Raoult’s law for a solution containing non-volatile solute. What type of deviation from
Raoult’s law is shown by a solution of chloroform and acetone and why?
Q.29.
(i)
(ii)
Q.30.
Define an ideal solution and write one of its characteristics.
Q.31.
Define azeotropes. What type of azeotrope is formed by negative deviation from Raoult’s law? Give
an example.
Q.32.
State the following:
(i) Raoult’s law in its general form in reference to solutions.
(ii) Henry’s law anbout partial pressure of a gas in a mixture.
Q.33.
(i)
Gas (A) is more soluble in water than Gas (B) at the same temperature. Which one of the two
gases will have the higher value of KH (Henry’s constant) and why?
In non-ideal solution, what type of deviation shows the formation of maximum boiling
azeotropes?
at
(ii)
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Why is an increase in temperature observed on mixing chloroform and acetone?
Why does sodium chloride solution freeze at a lower temperature than water?
What type of deviation is shown by a mixture of ethanol and acetone? What type of azeotrope is
formed by mixing ethanol and acetone?
Q.35.
Write two difference between a solution showing positive deviation and a solution showing negative
deviation from Raoult’s law.
Q.36.
Define the following terms:
(i) Abnormal molar mass
(ii) vant’s Hoff factor(i)
Q.37.
(i)
Q.39.
A solution prepared by dissolving 8.95 mg of a gene fragment in 35.3 mL of water has an osmotic
pressure of 0.335 torr at 25oC. Assuming that the gene fragment is a non-electrolyte, calculate its
molar mass.
Henry’s law constant (KH) for the solution of methane in benzene at 298 K is 4.27 ×105 mm Hg.
Calculate the solubility of methane in benzene at 298 K under 760 mm Hg.
M
Q.40.
State Raoult’s law for the solution containing volatile components. Write two differences between
an ideal solution and a non-ideal solution.
O
S
Q.38.
On mixing liquid X and liquid Y, volume of the resulting solution decreases. What type of
deviation from Raoult’s law is shown by the resulting solution? What change in temperature
would you observe after mixing liquids X and Y?
What happens when we place the blood cell in water (hypotonic solution)? Give reason.
Pu
(ii)
bl
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Q.34.
Q.41.
Derive the relationship between relative lowering of vapour pressure and molar mass of the solute.
Q.42.
When 1.5 g of a non-volatile solute was dissolved in 90 g of benzene, the boiling point of benzene
raised from 353.23 K to 353.93 K. Calculate the molar mass of the solute.
Q.43.
Explain the solubility rule “like dissolves like” in terms of intermolecular forces that in solutions.
Q.44.
Will the elevation in boiling point be same if 0.1 mol of sodium chloride or 0.1 mol of sugar is
dissolved in 1 L of water? Explain.
Q.45.
Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol-1) in
250 g of water. (Kf of water = 1.86 K kg mol-1)
Q.46.
At 25oC the saturated vapour pressure of water is 3.165 kPa (23.75 mm Hg). Find the saturated
vapour pressure of a 5% aqueous solution of urea (carbamide) at the same temperature.
(Molar mass of urea = 60.05 g mol-1)
Q.47.
Calculate the freezing point of a solution when 3 g of CaCl2 (M = 111 g mol-1) was dissolved in 100
9818536667
Solutions
Q.48.
23
g of water, assuming CaCl2 undergoes complete ionization. (Kf for water = 1.86 K kg mol-1)
3.9 g of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K.
Calculate the van’t Hoff factor and predict the nature of solute (associated or dissociated).
(Given: Molar mass of benzoic acid = 1.22 g mol-1, Kf for benzene = 4.9 K Kg mol-1)
Q.49.
A solution of glucose (Molar mass = 180g mol -1 ) in water has a boiling point of 100.20oC. Calculate
the freezing point of the same solution. Molal constants for water Kf and Kb are 1.86K kg mol -1 and
0.512K kg mol -1 respectively.
Q.50.
Calculate the boiling point of solution when 2 g of Na2SO4 ( M = 142 g mol-1) was dissolved in 50 g
of water, assuming Na2SO4 undergoes complete ionisation.
Calculate the mass of NaCl (molar mass = 58.5 g mol-1) to be dissolved in 37.2 g of water to lower
the freezing point by 2oC, assuming that NaCl undergoes complete dissociation.
ns
Q.51.
A solution containing 1.9 g per 100 mL of KCl (M = 74.5 g mol-1) is isotonic with a solution containing
3 g per 100 mL of urea (M = 60 g mol-1). Calculate the degree of dissociation of KCl solution. Assume
that both the solutions have same temperature.
Q.53.
At 300 K, 30 g of glucose, C6H12O6 present per litre in its solution has an osmotic pressure of
4.98 bar. If the osmotic pressure of another glucose solution is 1.52 bar at the same temperature,
calculate the concentration of the other solution.
Q.54.
Given alongside is the sketch of a plant for carrying out a process.
(i)
When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K.
Calculate the formula of sulphur (Sx).
[Kf for CS2 = 3.83 K kg mol-1, Atomic mass of sulphur = 32 g mol-1]
(ii) Blood cells are isotonic with 0.9 % sodium chloride solution. What happens if we place blood
cells in a solution containing
(a) 1.2% sodium chloride solution? (b) 0.4% sodium chloride solution?
M
Q.56.
Define the following terms:
(a)
Azeotrope
(b)
Osmotic pressure
(c)
Colligative properties
Calculate the molarity of 9.8% (w/w) solution of H2SO4 if the density of the solution is 1.02 g
mL-1. (Molar mass of H2SO4 = 98 g mol-1)[CBSE (F) 2014]
O
S
Q.55.
(i)
(ii)
Name the process occurring in the given plant.
To which container does the net flow of solvent take place?
Name one SPM which can be used in this plant.
Give one practical use of the plant.
Pu
(i)
(ii)
(iii)
(iv)
bl
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Q.52.
Q.57.
(i)
(ii)
Define the following terms:
(a)
Molarity
(b)
Molal elevation constant (Kb)
A solution containing 15 g urea (molar mass = 60 g mol-1) per litre of solution in water has the
same osmotic pressure (isotonic) as a solution of glucose (molar mass = 180 g mol-1) in water.
Calculate the mass of glucose present in one litre of its solution.
Q.58.
(i)
(ii)
Explain why on addition of 1 mol glucose to 1 litre water the boiling point of water increases.
Henry’s law constant for CO2 in water is 1.67 ×108 Pa at 298 K. Calculate the number of moles
of CO2 in 500 ml of soda water when packed under 2.53 ×105 Pa at the same temperature.
Q.59.
Discuss biological and industrial importance of osmosis.
Q.60.
(i)
Why a person suffering from high blood pressure is advised to take minimum quantity of
common salt?
9818536667
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24
Q.61.
(ii)
2 g of benzoic acid (C6H5COOH) dissolved in 25 g of benzene shows a depression in freezing
point equal to 1.62 K. Molal depression constant for benzene is 4.9 K kg mol-1. What is the
percentage association of acid if it forms dimer in solution?
(i)
(a)
Give reasons for the following:
At higher altitudes, people suffer from a disease called anoxia. In this disease, they become
weak and cannot think clearly.
When mercuric iodide is added to an aqueous solution of KI, the freezing point is raised.
0.6 mL of acitic acid (CH3COOH), having density 1.06 g mL-1, is dissolved in 1 litre of water.
The depression in freezing point observed for this strength of acid was 0.0205oC. Calculate the
van’t Hoff factor and the dissociation constant of acid.
M
O
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Pu
bl
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(b)
(ii)
9818536667
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25
PREVIOUS YEARS
EXPRESSING CONCENTRATION OF SOLUTIONS
Define the following term: Molality (m)
(Delhi 2017)
2.
Define the following term: Molarity (M) (Delhi 2017)
3.
Define the following term: Mole fraction.
(Delhi 2012,2009)
4.
State the main advantage of molality over molarity as the unit of concentration.
5.
Calculate the molarity of 9.8% (w/W) solution of H2SO4 if the density of the solution is 1.02 g mL-1.
(Molar mass of H2SO4 = 98 g mol-1) (AI 2014)
6.
Differentiate between molarity and molality of a solution. How can we change molality value of a solution
into molarity value ? (Delhi 2014)
7.
A solution of glucose (C6H12O6) in water is labelled as 10% by weight. What would be the molality of the
solution ?(Molar mass of glucose = 180 g mol-1)
(AI 2013)
8.
An antifreeze solution is prepared from 222.6 g of ethylene glycol (C2H4(OH)2)and 200 g of water.
Calculate the molality of the solution. If the density of this solution be 1.072 g mL-1 what will be the
molality of the solution ? (Delhi 2007)
9.
A solution of glucose (molar mass = 180 g mol-1) in water is labelled as 10% (by mass). What would be
the molality and molarity of the solution?(Density of solution = 1.2 g mL-1)
(AI 2014)
(Delhi 2009)
bl
ic
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1.
Pu
SOLUBILITY
State Raoult’s law for a solution containing volatile components. Write two characteristics of the solution
which obeys Raoult’s law at all concentrations.
[Delhi 2019]
11.
Aquatic animals are more comfortable in cold water than in warm water.
12.
13.
(Delhi 2018)
Gas (A) is more soluble in water than gas (B) at the same temperature. Which one of the two gases will
have the higher value of KH (Henry’s constant) and why ? (AI 2016)
Explain Henry’s law about dissolution of a gas in a liquid. (AI 2012)
The partial pressure of ethane over a saturated solution containing 6.56×10-2 g of ethane is 1 bar. If the
solution contains 5.0×10-2 g of ethane, then what will be the partial pressure of the gas ?
(AI 2012)
M
14.
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10.
15.
If N2 gas is bubbled through water at 293 K, how many millimoles of N2 gas would dissolve in 1 litre of
water? Assume that N2 exerts a partial pressure of 0.987 bar. Given that Henry’s law constant for N2 at
293 K is 76.48 K bar. (AI 2012)
16.
What concentration of nitrogen should be present in a glass of water at room temperature? Assume a
temperature of 25oC, a total pressure of 1 atmosphere and mole fraction of nitrogen in air of 0.78.
[KH for nitrogen =8.42×10-7 M/mm Hg] (AI 2009)
VAPOUR PRESSURE OF LIQUID SOLUTIONS
17.
Define Raoult’s law. (AI 2014)
18.
What is the similarity between Raoult’s law and Henry’s law ? 19.
Name the solution which follows Raoult’s law at all concentrations and temperatures. 9818536667
(Delhi 2014)
(AI 2014)
Solutions
26
20.
How is it formulated for solutions of non-volatile solutes ? (Delhi 2012)
21.
The vapour pressure of pure liquids A and B are 450 and 700 mm Hg respectively, at 350 K. Find out the
composition of the liquid mixture if total vapour pressure is 600 mm Hg. Also find the composition of the
vapour phase. (AI 2013)
IDEAL AND NON-IDEAL SOLUTIONS
22.
Write two characteristics of non-ideal solution.
[AI 2019]
23.
Define Ideal solution.
24.
In non-ideal solution, what type of deviation shows the formation of maximum boiling azeotropes?
(AI 2016)
25.
Some liquids on mixing form ‘azeotropes’. What are ‘azeotropes’ ? 26.
How is it that alcohol and water are miscible in all proportions ? 27.
What is meant by positive deviations from Raoult‘s law ? Give an example. What is the sign of ΔmixH for
positive deviation ? (Delhi 2015)
28.
What type of azeotrope is formed by positive deviation from Raoult’s law ?Give an example.
(Delhi 2015)
29.
What is meant by negative deviation from Raoult’s law ? Give an example. What is the sign of ΔmixH for
negative deviation ? (AI 2015)
30.
What type of azeotrope is formed by negative deviation from Raoult’s law ? Give an example.(AI 2015)
31.
What type of deviation is shown by a mixture of ethanol and acetone ? Give reason. 32.
Explain why a solution of chloroform and acetone shows negative deviation from Raoult’s law.
(Delhi 2011)
33.
What type of intermolecular attraction exists in each of the following pairs of compounds:
(i) n-hexane and n-octane (ii)
methanol and acetone
(Delhi 2010)
(Delhi 2014)
(AI 2007)
(AI 2014)
Pu
bl
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(Delhi 2017)
34.
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COLLIGATIVE PROPERTIES AND DETERMINATION OF MOLAR MASS
(a)
(b)
M
(c)
Draw the graph between vapour pressure and temperature and explain the elevation in boiling point
of a solvent in solution.
Determine the osmotic pressure of a solution prepared by dissolving 25 mg of K2SO4 in 2 litres of
water at 25°C assuming it to be completely dissociated. (Atomic masses K = 39 u ,S = 32 u, O= 16 u)
2 g of benzoic (C6H5COOH) dissolved in 25 g of benzene shows a depression constant for benzene
is 4.9 K kg mol-1 . what is the percentage association of acid if it forms dimer in solution? [AI 2019]
35.
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 (M = 180 g mol-1 ) in water.
(Given : Freezing point of pure water = 273.15 K) [Delhi 2019]
36.
Calculate the freezing point of a solution containing 60 g of glucose (Molar mass = 180 g mol-1) in 250 g
of water. (Kf of water = 1.86 K kg mol-1)
(Delhi 2018)
37.
Give reasons for the following : (Delhi 2018)
Measurement of osmotic pressure method is preferred for the determination of molar masses of
macromolecules such as proteins and polymers.
38.
Define Colligative properties.
(Delhi 2017)
39.
What are isotonic solutions ? (Delhi 2014)
40.
Define Molal elevation constant (Kb). (AI 2014)
9818536667
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27
41.
How is the vapour pressure of a solvent affected when a non-volatile solute is dissolved in it ?
(Delhi 2014)
42.
Define Osmotic pressure.
43.
44.
State the condition resulting in reverse osmosis. (AI 2007)
(i) Out of 1 M glucose and 2 M glucose, which one has a higher boiling point and why ?
(ii) What happens when the external pressure applied becomes more than the osmotic pressure of
solution ? (Delhi 2016)
45.
Blood cells are isotonic with 0.9% sodium chloride solution. What happens if we place blood cells in a
solution containing
(i) 1.2% sodium chloride solution ?
(ii)
0.4% sodium chloride solution ? (Delhi 2016)
46.
Why does a solution containing non-volatile solute have higher boiling point than the pure solvent ? Why
is elevation of boiling point a colligative property ? (AI 2015)
47.
Calculate the mass of compound (molar mass = 256 g mol-1) to be dissolved in 75 g of benzene to lower
its freezing point by 0.48 K. (Kf = 5.12 K kg mol-1). (Delhi 2014)
48.
18 g of glucose, C6H12O6 (Molar mass = 180 g mol-1)is dissolved in 1 kg of water in a sauce pan. At what
temperature will this solution boil ?(Kb for water = 0.52 K kg mol-1, boiling point of pure water = 373.15
K) (Delhi 2013)
49.
An aqueous solution of sodium chloride freezes below 273 K. Explain the lowering in freezing point of
water with the help of a suitable diagram. (Delhi 2013)
50.
Define the terms osmosis and osmotic pressure. Is the osmotic pressure of a solution a colligative property
? Explain. (Delhi 2011)
51.
List any four factors on which the colligative properties of a solution depend. 52.
What is the advantage of using osmotic pressure as compared to other colligative properties for the
determination of molar masses of solutes in solutions ? (AI 2010)
53.
Outer hard shells of two eggs are removed. One of the egg is placed in pure water and the other is placed
in saturated solution of sodium chloride. What will be observed and why ? (AI 2010)
54.
Find the boiling point of a solution containing 0.520 g of glucose (C6H12O6) dissolved in 80.2 g of water.
[Given: Kb for water = 0.52 K/m] (AI 2010)
ns
io
at
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bl
Pu
Describe how the molecular mass of a substance can be determined on the basis of osmotic pressure
measurement. (AI 2008)
A 10% solution (by mass) of sucrose in water has freezing point of 269.15 K. Calculate the freezing point
of 10% glucose in water, if freezing point of pure water is 273.15 K.
(Given: Molar mass of sucrose = 342 g mol-1, molar mass of glucose = 180 g mol-1) (Delhi 2017)
M
56.
(AI 2011)
O
S
55.
(AI 2013)
57.
30 g of urea (M = 60 g mol-1) is dissolved in 846 g of water. Calculate the vapour pressure of water for
this solution if vapour pressure of pure water at 298 K is 23.8 mm Hg. (AI 2017)
58.
Calculate the freezing point of the solution when 31 g of ethylene glycol (C2H6O2) is dissolved in 500 g
of water.(Kf for water = 1.86 K kg mol-1). (AI 2015)
59.
A solution containing 15 g urea (molar mass = 60 g mol-1) per litre of solution in water has the same
osmotic pressure (isotonic) as a solution of glucose (molar mass = 180 g mol-1) in water. Calculate the
mass of glucose present in one litre of its solution. (AI 2014)
60.
Calculate the boiling point elevation for a solution prepared by adding 10 g of CaCl2 to 200 g of water.
(Kb for water = 0.52 K kg mol-1, molar mass of CaCl2 = 111 g mol-1) (AI 2014)
61.
Some ethylene glycol, HOCH2CH2OH, is added to your car’s cooling system along with 5 kg of water. If
the freezing point of water-glycol solution is -15.0oC, what is the boiling point of the solution ?
(Kb = 0.52 K kg mol-1 and Kf = 1.86 K kg mol-1 for water) (Delhi 2014)
62.
1.00 g of a non-electrolyte solute dissolved in 50 g of benzene lowered the freezing point of benzene by
9818536667
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Solutions
0.40 K. The freezing point depression constant of benzene is 5.12 K kg mol-1. Find the molar mass of the
solute. (AI 2013,2008)
A 5% solution (by mass) of cane-sugar in water has freezing point of 271 K. Calculate the freezing point
of 5% solution (by mass) of glucose in water if the freezing point of pure water is 273.15 K.
[Molecular masses: Glucose C6H12O6 : 180 amu; Cane-sugar C12H22O11: 3.42 amu] (AI 2013)
64.
A solution of glycerol (C3H8O3) in water was prepared by dissolving some glycerol in 500 g of water.
This solution has a boiling point of 100.42oC while pure water boils at 100oC . What mass of glycerol was
dissolved to make the solution ? (Kb for water = 0.512 K kg mol-1) (Delhi 2012,2010)
65.
15.0 g of an unknown molecular material was dissolved in 450 g of water. The resulting solution was
found to freeze at -0.34oC. What is the molar mass of this material ?
(Kf for water = 1.86 K kg mol-1) (Delhi 2012)
66.
A solution containing 30 g of non-volatile solute exactly in 90 g of water has vapour pressure of 2.8 kPa
at 298 K. Further 18 g of water is added to this solution. This new vapour pressure becomes 2.9 kPa at
298K. Calculate
(i) the molecular mass of solute and
(ii)
vapour pressure of water at 298 K. (Delhi 2012)
67.
Calculate the boiling point of a solution prepared by adding 15.00 g of NaCl to 250.00 g of water.
(Kb for water = 0.512 K kg mol-1), (Molar mass of NaCl = 58.44 g) (Delhi 2011)
68.
A solution prepared by dissolving 8.95 mg of a gene fragment in 35.0 mL of water has an osmotic
pressure of 0.335 torr at 25oC. Assuming the gene fragment is a non-electrolyte, determine its molar
mass.
(AI,Delhi 2011)
69.
What would be the molar mass of a compound if 6.21 g of it dissolved in 24.0 g of chlororform to form
a solution that has a boiling point of 68.04oC. The boiling point of pure chloroform is 61.7oC and the
boiling point elevation constant, Kb for chloroform is 3.63oC/m
(Delhi 2011)
70.
What mass of NaCl must be dissolved in 65.0 g of water to lower the freezing point of 65.0 g of water
to lower the freezing point of water by 7.50oC? The freezing point depression constant (Kf)for water is
1.86oC/m. Assume van’t Hofff factor for NaCl is 1.87. (Molar mass of NaCl = 58.5 g mol-1). (AI 2011)
71.
Calcuate the boiling point of one molar aqueous solution (density 1.06 g mL-1) of KBr.
[Given: Kb for H2O = 0.52 K kg mol-1, atomic mass: K = 39, Br = 80]
72.
A solution prepared by dissolving 1.25 g of oil of winter green (methyl salicylate) in 99.0 g of benzene
has a boiling point of 80.31oC. Determine the molar mass of the compound. (B.pt. of pure benzene =
80.10oC and Kb for benzene = 2.53oC kg mol-1) (Delhi 2010)
io
at
ic
bl
Pu
O
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(AI 2011)
What mass of ethylene glycol (molar mass = 62.0 g mol-1) must be added to 5.50 kg of water to lower the
freezing point of water from 0oC to - 10.0oC? (Kf for water 1.86 K kg mol-1) (AI 2010)
M
73.
ns
63.
74.
100 mg of a protein is dissolved in just enough water to make 10.0 mL of solution. If this solution has an
osmotic pressure of 13.3 mm Hg at 25oC, what is the molar mass of the protein ?
(R = 0.0821 L atm mol-1 K-1 and 760 mm Hg = 1 atm.) (Delhi 2009)
[Ans: 13980.45 g mol-1]
75.
Calculate the amount of sodium chloride which must be added to one kilogram of water so that the
freezing point of water is depressed by 3 K.
[Given: Kf = 1.86 K kg mol-1, atomic mass: Na = 23.0, Cl = 35.5] (AI 2009)
76.
x g of a non-electrolytic compound (molar mass = 200) is dissolved in 1.0 L of 0.05 M NaCl aqueous
solution. The osmotic pressure of this solution is found to be 4.92 atm at 27oC. Calculate the value of x.
Assume complete dissociation of NaCl and ideal behaviour of the solution.
(R = 0.0821 L atm mol-1 K-1)
(AI 2009)
77.
Calculate the freezing point of a solution containing 18 g glucose, C6H12O6 and 68.4 g sucrose, C12H22O11
in 200 g of water. The freezing point of pure water is 273 K and Kf for water is 1.86 K m-1. (AI 2009)
9818536667
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29
78.
Calculate the temperature at which a solution containing 54 g of glucose, (C6H12O6), in 250 g of water will
freeze. (Kf for water = 1.86 K mol-1 kg). (Delhi 2008)
79.
A solution containing 8 g of a substance in 100 g of diethyl ether boils at 36.86oC, whereas pure ether
boils at 35.60oC. Determine the molecular mass of the solute. (For ether Kb = 2.02 K kg mol-1) (AI 2008)
80.
A 0.1539 molal aqueous solution of cane sugar (mol. mass = 342 g mol-1) has a freezing point of 271 K
while the freezing point of pure water is 273.15 K. What will be the freezing point of an aqueous solution
containing 5 g of glucose (mol. mass = 180 g mol-1) per 100 g of solution. (AI 2007)
ABNORMAL MOLAR MASSES
Elevation of boiling point of 1 M KCl solution is nearly double than that of 1 M sugar solution.
(Delhi 2018)
82.
Define Van’t Hoff factor.
83.
Define Abnormal molar mass.
84.
What type of values cant it have if in forming the solution the solute molecular undergo
(i) dissociation
(ii)
association 85.
Assuming complete dissociation , calculate the expected freezing point of a solution prepared by
dissolving 6.00 g of Glauber’s salt. Na2SO4.10H2O in 0.100 kg of water. (Kf for water = 1.86 K kg mol-1,
atomic masses:Na = 23, S = 32, O = 16, H = 1) (AI 2014)
86.
A 1.00 molal aqueous solution of trichloroacetic acid (CCl3COOH) is heated to its boiling point. The
solution has the boiling point of 100.18oC. Determine the van’t Hoff factor for trichloroacetic acid. (Kb
for water = 0.512 K kg mol-1)
(Delhi 2012)
87.
Calculate the freezing point of solution when 1.9 g of MgCl2 (M = 95 g mol-1) was dissolved in 50 g of
water, assuming MgCl2 undergo complete ionization.(Kf for water = 1.86 K kg mol-1)
(Delhi 2016)
88.
When 2.56 g of sulphur was dissolved in 100 g of CS2, the freezing point lowered by 0.383 K. Calculate
the formula of sulphur (Sx). (Kf the CS2 = 3.83 K kg mol-1, atomic mass of sulphur = 32 g mol-1)
(Delhi 2016)
89.
90.
io
(AI 2014)
Pu
bl
ic
at
(Delhi 2017)
Calculate the boiling point of solution when 4 g of MgSO4 (M = 120 g mol-1) was dissolved in 100 g of
water, assuming MgSO4 undergoes complete ionization.(Kb for water = 0.52 K kg mol-1)
(AI 2016)
3.9 of benzoic acid dissolved in 49 g of benzene shows a depression in freezing point of 1.62 K. Calculate
the van’t Hoff factor and predict the nature of solute (associated or dissociated).
(Given: Molar mass of benzoic acid = 122 g mol-1, Kf for benzene = 4.9 K kg mol-1)
(Delhi 2015)
Calculate the mass of NaCl (molar = 58.5 g mol-1) to be dissolved in 37.2 g of water to lower the freezing
point by 2oC, assuming that NaCl undergoes complete dissociation.
( Kf for water = 1.86 K kg mol-1) (AI 2015)
M
91.
(Delhi 2017,2012)
O
S
ns
81.
92.
Determine the osmotic pressure of a solution prepared by dissolving 2.5×10-2 g of K2SO4 in 2 L of water
at 25oC , assuming that it is completely dissociated.
(R = 0.0821 L atm K-1 mol-1, molar mass of K2SO4 = 174 g mol-1) (Delhi 2013)
93.
Calculate the amount of KCl which must be added to 1 kg of water so that the freezing point is depressed
by 2 K (the Kf for water = 1.86 K kg mol-1). (Delhi 2012)
94.
Calculate the freezing point of an aqueous solution containing 10.50 g of MgBr2 in 200 g of water.
(Molar mass of MgBr2 = 184 g mol-1) (Kf for water = 1.86 K kg mol-1) (Delhi 2011)
95.
A 0.561 m solution of an unknown electrolyte depresses the freezing point of water by 2.93oC. What is
van’t Hoff factor for this electrolyte ?
The freezing point depression constant (Kf) for water is 1.86oC kg mol-1. (AI 2011)
96.
Phenol associates in benzene to a certain extent to form a dimer. A solution containing 20 g of phenol in
9818536667
Solutions
30
1 g of benzene has its freezing point lowered by 0.69 K. Calculate the fraction of phenol that has dimerised.
[Given Kf for benzene = 5.1 K m-1] (Delhi 2011)
An aqueous solution containing 12.48 g of barium chloride in 1.0 kg of water boils at 373.0832 K.
Calculate the degree of dissociation of barium chloride.
[Given Kb for H2O = 0.52 K m-1; Molar mass of BaCl2 = 208.34 g mol-1]
(Delhi 2011)
98.
A decimolar solution of potassium ferrocyanide K4[Fe(CN)6] is 50% dissociated at 300 K. Calculate the
value of van’t Hoff factor for potassium ferrocyanide. (Delhi 2010)
99.
The boiling point elevation of 0.30 g acetic acid in 100 g benzene is 0.0633 K. Calculate the molar mass
of acetic from this data. What conclusion can you draw about the molecular state of the solute in the
solution ? [Given Kb for benzene = 2.53 K kg mol-1] (AI 2008)
100.
The freezing point of a solution containing 0.2 g of acetic acid in 20.0 g of benzene is lowered by 0.45oC.
Calculate.
(i) the molar mass of acetic acid from this data
(ii)
van’t Hoff factor
[For benzene, Kf = 5.12 K kg mol-1]
What conclusion can you draw from the value of van’t Hoff factor obtained ? (AI 2008)
101.
(i)
The depression in freezing point of water observed for the same molar concentration of acetic acid,
trichloroactic acid and trifluroactic acid increases in the order as stated above. Explain.
Calculate the depression in freezing point of water when 20.0 g of CH3CH2CHClCOOH is added to
500 g of water. [Given: Ka = 1.4×10-3, Kf = 1.86 K kg mol-1]
(Delhi 2008)
at
(ii)
io
ns
97.
bl
ic
2020 Board Questions
Pu
Question 1:
(A) Both Assertion (A) and Reason (R) are correct statements, and Reason (R) is the correct explanation
of the Assertion (A).
(B) Both Assertion (A) and Reason (R) arte correct statements, but Reason (R) is not the correct
explanation of the Assertion (A).
(C) Assertion (A) is correct, but Reason (R) is wrong statement.
(D) Assertion (A) is wrong, but Reason (R) is correct statement.
2.
State Raoult’s law for a solution containing volatile components. What is the similarity between Raoult’s
law and Henry’s law?
[Delhi 2020]
A 0.01 m aqueous solution of AlCl3 freezes at –0.068 oC. Calculate the percentage of dissociation. [Given:
Kf for water = 1.86 K kg mol-1]
[Delhi 2020]
M
3.
Assertion : 0.1 M solution of KCl has greater osmotic pressure than 0.1 M solution of glucose at same
temperature.
Reason : In solution, KCl dissociates to produce more number of particles.
[Delhi 2020]
O
S
1.
4.
What happens when
(i) a pressure greater than osmotic pressure is applied on the solution side separated from solvent
by a semipermeable membrane?
(ii) acetone is added to pure ethanol?
[AI 2020]
5.
State Henry’s Law. Calculate the solubility of CO2 in water at 298 K under 760 mm Hg.
(KH for CO2 in water at 298 K is 1.25 × 106 mm Hg)
6.
The freezing point of a solution containing 5g of benzoic acid (M = 122 g mol ) in 35 g of benzene is
depressed by 2.94 K. What is the percentage association of benzoic acid if it forms a dimer in solution?
(Kf for benzene = 4.9 K kg mol-1).
[AI 2020]
-1
9818536667
[AI 2020]
Solutions
A solution of a pair of volatile liquids A and B
shows negative deviation from Raoult’s law.
Which of the following holds true for it?
(a) pA < xA pAo and pB < xB pBo.
(b) The intermolecular forces A–A, B–B < A–B.
(c) Both ∆Hmix and ∆Vmix are negative.
(d) All of these.
In 100 g of naphthalene, 2.423 g of S was
dissolved. melting point of naphthalene =
80.1 °C. ∆Tf = 0.661 °C. Lf = 35.7 cal g−1 of
naphthalene. Molecular formula of sulphur
added is
(a) S2
(b) S4
(c) S6
(d) S8
10.
Which of the following statements is not correct
for an ideal binary liquid solution AB (xA = mole
fraction of A in vapor phase; xB = mole fraction
of B in vapor phase)?
(a) A plot between ptotal and xB is linear.
(b) A plot between ptotal and xA is linear.
(c) A plot between 1/ptotal and xA is linear.
(d) A plot between ptotal and 1/xA is non-linear.
Ethylene glycol is added to water as antifreeze.
It will
(a) decrease the freezing point of water in winter
and increase the boiling point of water in
summer.
(b) only decrease the freezing point of water.
(c) only increase the boiling point of water.
(d) be used for cleaning the radiator in a car.
11.
io
A liquid is in equilibrium with its vapor at its
boiling point. On an average, the molecules in
the two phases have equal
(a) intermolecular forces.
(b) potential energy.
(c) total energy.
(d) kinetic energy.
ic
3.
Which has the highest freezing point at 1 atm?
(a) 0.1 molal NaCl solution
(b) 0.1 molal BaCl2 solution
(c) 0.1 molal sugar solution
(d) 0.1 molal FeCl3 solution
at
2.
ns
9.
MULTIPLE CHOICE QUESTIONS
1.
31
bl
In which mode of expression, the concentration
of solution remains independent of temperature?
(a) Molarity
(b) Normality
(c) Formality
(d) Molality
5.
Van′t Hoff factor for 0.1 M ideal solution is
(a) 0.1
(b) 1
(c) −0.01
(d) None of these.
13.
Solutions which distil without change in
composition in liquid and vapor phase are called
(a) amorphous.
(b) azeotropic mixtures.
(c) supersaturated. (d) ideal.
14.
Camphor is often used in molecular mass
determination because
(a) it is readily available.
(b) it has a very high cryoscopic constant.
(c) it is volatile.
(d) it is solvent for organic substances.
The azeotropic mixture of water (boiling point
100 °C) and HCl (boiling point 85 °C) boils at
108.5 °C. When this mixture is distilled, it is
possible to obtain
(a) pure HCl.
(b) pure water.
(c) pure water as well as HCl.
(d) neither HCl nor water in their pure states.
15.
A pressure cooker reduces cooking time because
(a) the heat is more evenly distributed.
(b) the higher pressure tenderizes the food.
(c) the boiling point of water inside the cooker
is elevated.
(d) the boiling point of water inside the cooker
is depressed.
16.
If we place the blood cells in a solution containing
less than 0.9% (m/V) sodium chloride. They
would swell. This is because:
The average osmotic pressure of human blood is
7.8 bar at 37 °C. What is the concentration of an
aqueous NaCl solution that could be used in the
blood stream?
(a) 0.15 mol L−1
(b) 0.30 mol L−1
(c) 0.60 mol L−1
(d) 0.45 mol L−1
M
7.
8.
An azeotropic solution of two liquids has boiling
point lower than that of either of them if it
(a) shows a negative deviation from Raoult’s
law.
(b) shows a positive deviation from law.
(c) shows no deviation from Raoult’s law.
(d) is saturated.
O
S
Pu
4.
6.
12.
If molality of aqueous solution of H2SO4 is 2,
then normality of solution is (density of solution
= 1.2 g mL−1)
(a) 8.02
(b) 4.01
(c) 2.02
(d) 9.01
9818536667
Solutions
the solution is hypotonic
the solution is isotonic
the solution is hypertonic
none of these
(c) −0.372 °C.
On dissolving sugar in water at room temperature
solution feels cool to touch. Under which of the
following cases dissolution of sugar will be
most rapid?
(a) Sugar crystals in cold water
(b) Sugar crystals in hot water
(c) Powdered sugar in cold water
(d) Powdered sugar in hot water
18.
Considering the formation, breaking and
strength of hydrogen bond, predict which of
the following mixtures will show a positive
deviation from Raoult’s law?
(a) Methanol and acetone
(b) Chloroform and acetone
(c) Nitric acid and water
(d) Phenol and aniline
Formation of a solution from two components
can be considered as
(i) pure solvent → separated solvent molecules,
∆H1
(ii) pure solute → separated solute molecules,
∆H2
(iii) separated solvent and solute molecules →
solution, ∆H3. Solutions so formed will be
ideal if
(a) ∆Hsoln = ∆H1 + ∆H2 + ∆H3
(b) ∆Hsoln = ∆H1 + ∆H2 − ∆H3
(c) ∆Hsoln = ∆H1 − ∆H2 − ∆H3
(d) ∆Hsoln = ∆H3 − ∆H1 − ∆H2
24.
If mole fraction of H2O in aqueous solution
of glucose is, 0.8 then molality of solution (in
molal) is
(a) 13.88
(b) 13.08
(c) 12.11
(d) 8.88
Which of the following aqueous solutions
should have the highest boiling point?
(a) 1.0 M NaOH
(b) 1.0 M Na2SO4
(c) 1.0 M NH4NO3 (d) 1.0 M KNO3
25.
Pure water boils at 99.725 °C at Shimla. If Kb
for water is 0.51 °C molal−1, the boiling point of
0.69 molal urea solution will be
(a) 100.35 °C
(b) 100.08 °C
(c) 99.37 °C
(d) None of these
bl
ic
19.
23.
at
17.
(d) + 0.372 °C.
ns
(a)
(b)
(c)
(d)
io
32
20.
26.
At equilibrium the rate of dissolution of a solid
solute in a volatile liquid solvent is _______.
(a) less than the rate of crystallisation
(b) greater than the rate of crystallisation
(c) equal to the rate of crystallisation
(d) zero
27.
One kilogram of sea water sample contains 6
mg of dissolved O2. The concentration of O2 in
ppm in the sample is:
(a) 0.06
(b) 60
(c) 6
(d) 0.6
28.
Mole fraction of the solute in a 100 molal
aqueous solution is:
(a) 0.1770
(b) 0.0177
(c) 0.0344
(d) 1.7700
29.
Low concentration of oxygen in the blood and
tissues of people living at high altitude is due to
_______.
(a) low temperature
(b) low atmospheric pressure
(c) high atmospheric pressure
(d) both low temperature and high atmospheric
pressure
30.
A solution of chloroform in diethylether:
(a) obeys Raoult’s law
(b) shows a positive deviation from Raoult’s
M
O
S
Pu
Which of the following statements is false?
(a) Two different solutions of sucrose of same
molality prepared in different solvents will
have the same depression in freezing point.
(b) The osmotic pressure of a solution is given
by the equation π = CRT (where C is the
molarity of the solution).
(c) Decreasing order of osmotic pressure
for 0.01 M aqueous solutions of barium
chloride, potassium chloride, acetic acid and
sucrose is
BaCl2 > KCl > CH3COOH > sucrose.
(d) According to Raoult’s law, the vapour
pressure exerted by a volatile component of
a solution is directly proportional to its mole
fraction in the solution.
21.
Increasing the temperature of an aqueous
solution will cause
(a) decrease in molality.
(b) decrease in molarity.
(c) decrease in mole fraction.
(d) decrease in %w/w.
22.
The molal freezing point constant of water is
1.86 °C molal−1. Therefore, the freezing point
of 0.1 M NaCl solution in water is expected to
be
(a) −1.86 °C.
(b) −0.186 °C.
9818536667
Solutions
law
(c) shows a negative deviation from Raoult’s
law
(d) behaves like a near ideal solution
33
MgCl2 solution is ________.
(a) the same
(b) about twice
(c) about three times (d) about six times
An unripe mango placed in a concentrated salt
solution to prepare pickle, shrivels because
______.
(a) it gains water due to osmosis
(b) it loses water due to reverse osmosis
(c) it gains water due to reverse osmosis
(d) it loses water due to osmosis
The elevation in boiling point of a solution of
13.44 g of CuCl2 in 1 kg of water is (Given Kb
= 0.52 K molal−1, molecular weight of CuCl2 =
134.4 g mol−1.)
(a) 0.05 K
(b) 0.1 K
(c) 0.16 K
(d) 0.21 K
39.
At a given temperature, osmotic pressure of a
concentrated solution of a substance_______.
(a) is higher than that of a dilute solution
(b) is lower than that of a dilute solution
(c) is same as that of a dilute solution
(d) cannot be compared with osmotic pressure
of dilute solution
Benzene (C6H6, 78 g mol1) and toluene (C7H8,
92 g mol1) form an ideal solution. At 60 °C the
vapor pressure of pure benzene and pure toluene
are 0.507 atm and 0.184 atm, respectively. The
mole fraction of benzene in a solution of these
two chemicals that has a vapor pressure of 0.350
atm at 60 °C is
(a) 0.514
(b) 0.690
(c) 0.486
(d) 0.190
40.
33.
io
32.
The values of Van’t Hoff factors for KCl, NaCl
and K2SO4, respectively, are_______.
(a) 2, 2 and 2
(b) 2, 2 and 3
(c) 1, 1 and 2
(d) 1, 1 and 1
ic
at
The volumes of 4 N HCl and 10 N HCl required
to make 1 L of 6 N HCl are
(a) 0.75 L of 5 N HCl and 0.25 L of 10 N HCl
(b) 0.25 L of 4 N HCl and 0.75 L of 10 N HCl
(c) 0.67 L of 4 N HCl and 0.33 L of 10 N HCl
(d) 0.80 L of 4 N HCl and 0.20 L of 10 N HCl
ns
38.
31.
bl
Pu
Solution A contains 7 g L−1 MgCl2 and solution
B contains 7 g L−1 of NaCl. At room temperature,
the osmotic pressure of
(a) solution A is greater than B.
(b) both have the same osmotic pressure.
(c) solution B is greater than A.
(d) cannot be determined.
M
35.
At 334 K the vapor pressure of benzene (C6H6)
is 0.526 atm and that of toluene (C7H8) is 0.188
atm. In a solution containing 0.5 mol of benzene
and 0.5 mol of toluene, what is the vapor
pressure of toluene above the solution at 334 K?
(a) 0.188 atm
(b) 0.10 atm
(c) 0.357 atm
(d) 0.094 atm
O
S
34.
36.
Molal elevation constant is calculated from the
enthalpy of vapourisation ( ∆ vap H ) and boiling
point of the pure solvent (T0) using the relation:
M A RT02
1000 RT02
(a) K b =
(b) K b =
1000 ∆ vap H
M A ∆ vap H
(c) K b =
37.
41.
∆ vap H
1000 M A RT02
(d) K b =
42.
A person is considered to be suffering from
lead poisoning if its concentration in him is
more than 10 µg of lead per deciliter of blood.
Concentration in parts per billion parts is
(a) 1
(b) 10
(c) 100
(d) 1000
43.
The pH of 1 M solution of a weak monobasic
acid (HA) is 2. Then, the van’t Hoff factor is
(a) 1.01
(b) 1.02
(c) 1.10
(d) 1.20
44.
A substance is deliquescent if its vapor pressure
(a) is less than that of water vapor in the air.
(b) is more than that of water vapor in the air.
(c) is equal to that of water vapor in the air.
(d) is equal to atmospheric pressure.
45.
A student has 100 mL of 0.1 M KCl solution. To
make it 0.2 M, he has to
(a) evaporate 50 mL of the solution.
(b) add 0.01 mol of KCl.
(c) use both a and b.
(d) use neither a nor b.
46.
Which of the following statements is false?
1000 M AT02
∆ vap HR
In comparison to a 0.01 M solution of glucose,
the depression in freezing point of a 0.01 M
When mercuric iodide is added to the aqueous
solution of potassium iodide, the
(a) freezing point is raised.
(b) freezing point is lowered.
(c) freezing point does not change.
(d) boiling point does not change.
9818536667
Solutions
47.
The system that forms maximum boiling
azeotropes is:
(a) ethyl alcohol-water
(b) benzene-toluene
(c) acetone-chloroform
(d) carbon disulphide-acetone
The value of Henry’s constant KH is _________.
(a) greater for gases with higher solubility
(b) greater for gases with lower solubuility
(c) constant for all gases
(d) not related of the solubility of gases.
49.
Which of the following factor(s) affect the
solubility of a gaseous solute in the fixed volume
of liquid solvent?
(i) nature and solute (ii) temperature (iii)
pressure
(a) (i) and (iii) at constamnt T
(b) (i) and (ii) at constant P
(c) (ii) and (iii) only
(d) (iii) only
51.
Assertion: Molarity of a solution in liquid state
changes with temperature.
Reason: The volume of a solution changes with
change in temperature.
52.
Assertion: If more volatile liquid is added to
another liquid, vapour pressure of solution will
be greater than that of pure solvent.
Reason: Vapour pressure of solution is entirely
due to solvent molecules.
53.
Assertion: When NaCl is added to water a
depression in freezing point is observed.
Reason: The lowering of vapour pressure of a
solution causes depression in the freezing point.
54.
ic
Pu
bl
55.
Assertion: The solubility of a gas in a liquid
increases with increase of pressure.
Reason: The solubility of a gas in a liquid is
directly proportional to the pressure of the gas.
56.
Intermolecular forces between two benzene
molecules are nearly of same strength as those
between two toluene molecules. For a mixture
of benzene and toluene, which of the following
are not true?
zero
(a) ∆ mix H =
zero
(b) ∆ mixV =
(c) These will form minimum boiling azeotrope
(d) These will not from ideal solutions
Assertion: The vapour pressure of a liquid
decreases if some non-volatile solute is dissolved
in it.
Reason: The relative lowering of vapour
pressure of a solution containing a non-volatile
solute is equal to the mole fraction of the solute
in the solution.
57.
Assertion: Molecular mass of polymers cannot
be calculated using boiling point or freezing
point method.
Reason: Polymers solutions do not possess a
constant boiling point or freezing point.
ASSERTION-REASONING TYPE
58.
Assertion: The boiling point of 0.1 M urea solution is less than that of 0.1 M KCl solution.
Reason: Elevation of boiling point is directly
proportional to the number of species present in
the solution.
59.
Assertion: Non-ideal solutions always from
azeotropes.
Reason: Boiling point of an azeotrope may
be higher or lower than boiling points of both
components.
60.
Assertion: Lowering of vapour pressure is
directly proportional to osmotic pressure of the
M
O
S
50.
Assertion: When a solution is separated from
the pure solvent by a semipermeable membrane,
the solvent molecules pass through it from pure
solvent side to the solution side.
Reason: Diffusion of solvent occurs from a
region of high concentration solution to a region
of low concentration solution.
at
48.
(d) Assertion is wrong statement but reason
is correct statement.
ns
(a) Units of atmospheric pressure and osmotic
pressure are the same.
(b) In reverse osmosis, solvent molecules move
through a semipermeable membrane from a
region of lower concentration of solute to a
region of higher concentration.
(c) The value of molal depression constant
depends on nature of solvent.
(d) Relative lowering of vapour pressure, is a
dimensionless quantity.
io
34
In the following questions a statement of assertion
followed by a statement of reason is given. Choose the
correct answer out of the following choices.
(a) Assertion and reason both are correct
statements and reason is correct
explanation for assertion.
(b) Assertion and reason both are correct
statements but reason is not correct
explanation for assertion.
(c) Assertion is correct statement but reason
is wrong statement.
9818536667
Solutions
solution.
Reason: Osmotic pressure is a colligative
property.
∆Vmix = Negative but ∆Hmix = Positive.
(b) For solutions showing negative deviations,
the interactions between the components are
greater than the pure components.
(c) For solutions showing negative deviations,
∆Vmix = positive but ∆Hmix = negative.
(d) For solutions showing negative deviations,
∆Vmix and ∆Hmix are positive.
LINKED COMPREHENSION TYPE
65.
ns
Vapor pressure of a solution of heptane and
octane is given by the equation: p(solution) (mm
Hg) = 30 + 70x, where x is the mole fraction of
heptane. Vapor pressure of pure octane is
(a) 100 mm Hg
(b) 70 mm Hg
(c) 30 mm Hg
(d) 1.86 mm Hg
io
Paragraph for Questions 66 to 68: A solution is said to be
ideal if each of its components obey Raoult’s law for the
entire composition range. The law states that the vapor
pressure of any component in the solution depends on
the mole fraction of that component in the solution and
vapor pressure of that component in the pure state.
Solutions are non-ideal if they do not obey Raoult’s law
over the entire composition range. The vapor pressure
of the solution is either higher or lower than that
predicted by Raoult’s law. Depending on the type of
deviation from ideal behavior, non-ideal solutions may
be classified as showing negative deviation (lower vapor
pressure than predicted) or positive deviation (higher
vapor pressure than predicted). However, in either case,
corresponding to a particular composition, they form
constant boiling mixtures called azeotropes.
M
O
S
Pu
bl
ic
at
Paragraph for Questions 61 to 65: The pressure exerted
by the vapor when in equilibrium with a liquid or a
solution at a particular temperature is known as vapor
pressure. When two (or more) components of a liquid
solution evaporate, the vapor contains molecules of
each substance. All liquid solutions of non-volatile
solutes (solutes that have no tendency to evaporate)
have lower vapor pressures than their pure solvents.
The vapor pressure of such a solution is proportional
to how much of the solution actually consists of the
solvent. This proportionality is given by Raoult’s law
(also known as the vapor pressure– concentration
law) which says that the vapor pressure of the solution
equals the mole fraction of the solvent multiplied by
its vapor pressure when pure. In a binary solution of
components A and B, if the interactive forces between
A–A, B–B and A–B are same the solution is ideal.
Practically, no solution is ideal. A non-ideal solution
is that solution in which solute and solvent molecules
interact with one another with a different force than
the forces of interaction between the molecules of the
pure components. If for the two components A and B,
the forces of interaction between A and B molecules are
less than those between the A–A and B–B, the non-ideal
solutions have positive deviations. On the other hand, if
the forces of interaction between A and B molecules are
more than those between A–A and B–B, the non-ideal
solutions have negative deviations.
61.
If two liquids A and B form an ideal solution,
then
(a) the Gibbs energy of mixing is zero.
(b) the entropy of mixing is zero.
(c) the enthalpy of mixing is zero.
(d) the entropy of mixing is zero.
35
62.
Vapor pressure of dilute aqueous solution of
glucose is 750 mm Hg at 373 K. The mole
fraction of the solute is
(a) 1/75
(b) 75/76
(c) 1/76
(d) 1/10
63.
The vapor pressure of a pure liquid A is 30 mm
Hg at 300 K. The vapor pressure of this liquid in
solution with liquid B is 24 mm Hg. The mole
fraction of A in solution obeying Raoult’s law is
(a) 0.4
(b) 0.3
(c) 0.5
(d) 0.8
64.
66.
Which of the following mixtures do you expect
will show positive deviation from Raoult’s law?
(a) Benzene + Acetone
(b) Benzene + Choloroform
(c) Benzene + Carbon tetrachloride
(d) Benzene + Ethanol
67.
An azeotropic solution of two liquids has boiling
point higher than either of the two liquids when
it
(a) is saturated.
(b) shows a negative deviation from Raoult’s
law.
(c) shows a positive deviation from Raoult’s
law.
(d) shows no deviation from Raoult’s law.
68.
A solution has 1:4 mole ratio of heptanes
to hexane.The vapor pressure of the pure
hydrocarbons at 20 °C are 440 mm Hg for
heptane and 120 mm Hg for hexane.The mole
fraction of pentane in the vapor phase would be
(a) 0.200
(b) 0.478
Whichof the following statements is correct for
non-ideal solutions?
(a) For solutions showing positive deviations,
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(c) 0.549
(d) 0.786
Paragraph for Questions 69 to 73: On dissolving 68.4 g
of sucrose in 1 kg of water, a solution of sucrose with
molar mass 342 g mol−1 is formed. Kf for water is 1.86 K
kg mol−1 and vapor pressure of water at 298 K is 0.024
atm.
69.
The vapor pressure of the solution at 298 K will
be
(a) 0.230 atm.
(b) 0.233 atm.
(c) 0.236 atm.
(d) 0.0239 atm.
The osmotic pressure of the solution at 298 K
will be
(a) 4.29 atm.
(b) 4.49 atm.
(c) 4.69 atm.
(d) 4.89 atm.
71.
The freezing point of the solution will be
(a) −0.684 °C.
(b) −0.342 °C.
(c) −0.372 °C.
(d) −0.186 °C.
72.
The mass of sodium chloride that should be
dissolved in the same amount of water to get the
same freezing point will be
(a) 136.8 g
(b) 32.2 g
(c) 5.85 g
(d) 11.60g
73.
If on dissolving the above amount of NaCl in
1 kg of water, the freezing point is found to be
−0.344 °C, the percentage dissociation of NaCl
in the solution is
(a) 75%
(b) 80%
(c) 85%
(d) 90%
76.
blue colour forms in side ‘x’
blue colour forms in side ‘y’
blue colour forms on both sides
No blue colour formation
By applying external pressure osmosis can be
stopped it should be applied to –
(a) side ‘x’
(b) side ‘y’
(c) equal on both the sides
(d) can not be stopped by applying external
pressure
Paragraph for Questions 77 to 80: According
to Raoult’s law partial pressure of any volatile
constituent of a solution at a constant temperature
is equal to the vapour pressure of pure constituent
multiplied by mole-fraction of that constituent in the
solution.
This law is the major deciding factor whether a
solution will be ideal or non-ideal. Ideal solution
always obey Raoult’s law at energy range of
concentration.
A liquid mixture of benzene & toluene is
composed of 1 mol of benzene & 1 mol of
toluene. Benzene & toluene mixture behave
0
0
ideally. Given p t = 4.274 kN/m2 ; p b = 13.734 KN/m2
Pu
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70.
(a)
(b)
(c)
(d)
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36
M
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S
Paragraph for Questions 74 to 76: FeCl3 on reaction
with K4 [Fe(CN)6] in aqueous solution gives blue
colour, according the equation
4FeCl3 + 3K4[Fe(CN)6] → Fe4[Fe(CN)6]3 + 12 KCl
At 300 K two aqueous solution of K4[Fe(CN)6]
& FeCl3 with equal concentrations 0.1 M. These
two solutions are separated by a semipermeable
membrane AB as shown in figure.
0.1M
A
K4[Fe(CN)6]
side'x'
where subscript t & b stands for toluene & benzene
respectively.
77.
If pressure over mixture at 300 K is reduced at
what pressure does the first vapour form ?
(a) 18.008 KN/m2
(b) 9.004 KN/m2
(c) 13.05 KN/m2
(d) 3.003 KN/m2
78.
What is the composition of first trace of
vapour formed in terms of mole-fraction of
toluene –
(a) 0.2373
(b) 0.7627
(c) 0.333
(d) 0.67
79.
If the pressure is further reduced, at what
pressure does last trace of liquid disappear –
(a) 9.004 KN/m2
(b) 6.519 KN/m2
2
(c) 3.03 KN/m
(d) None of these
80.
What will be the mole-fraction of toluene in last
trace of liquid ?
(a) 0.2373
(b) 0.7627
(c) 0.333
(d) 0.67
0.1M
FeCl3
side'y'
B
74.
75.
What is correct –
(a) side ‘x’ is hypotonic
(b) side ‘y’ is hypotonic
(c) both are isotonic
(d) None of these
What is true about the solutions –
MATRIX-MATCH TYPE
Match the statements in Column I labeled as (A), (B),
(C) and (D) with those in Column II labeled as (p), (q),
(r), (s) and (t). Any given statement in Column I can
9818536667
Solutions
Column II
(p) 0.537
(q) 0.0096
(C) Mole fraction of H2SO4
(D) Mass fraction of H2SO4
(r) 0.05
(s) 0.515
82.
(B) i < 1
(C) i = 1
(D) i = 0
(q) Colloidal solution
(r) Not possible
(s) Solution of glucose + H2O
83.
Column I
(A) Relative lowering of
solute
(B) For electrolyte CaSO4
(C) For ideal Solution
(D) For NaHCO3
88.
O
S
Match the compounds with the nature of curves
the vapor pressure vs. mole fraction in aqueous
solution.
Column I
Column II
(p) Increases continuously
(A) Li2CO3
M
(q) Decreases continuously
(B) KCl
(C) Na2SO4⋅10H2O (r) First increases and then decreases
(D) NH4NO3
(s) Increases but not continuously
Column II
(p) XA = YA
(B) Azeotropic mixture
(q) XA < YA
0
(C) Equimolar mixture of (r) XB < YB
A & B with PA0 < PB0
(D) Equimolar mixture of (s) YB > YA
A & B with PA0 = PB0
TRUE or FALSE
89.
Solubility of a gas in a liquid solution as per
Henry law is a function of the partial pressure of
the gas at constant temperature.
90.
Mole fraction of the gas in a solution as per
Henry law is proportional to the partial pressure
of the gas at constant temperature.
91.
As per Henry law higher the value of kH at a
given partial pressure and temperature lower is
the solubility of the gas in the liquid.
92.
For solution of volatile liquids, the partial vapour
pressure of each component in the solution is
directly proportional to its mole fraction
93.
Always there will be lowering of vapour
pressure on addition of non-volatile solute to a
solvent
85.
Match the solvents with the colligative
properties.
Column I
Column II
(A) 0.1 M Glucose
(p) Solution with lowest
solution
freezing point
(B) 0.1 M Sucrose
(q) Solution with highest
solution
freezing point
(C) 0.1 M CaCl2 solution (r) Solution with lowest
osmotic pressure
(D) 0.1 M Ca3(PO4)2
(s) Solution with highest
osmotic pressure
solution
(q) i = 1
(r) i > 1
(s) i = 3
Column I
(A) PA > PB0
bl
Pu
84.
Column II
(p) Mole fraction of V.P.
For an ideal binary liquid solution of A & B. PA0
= pure vapour pressure of A. PB0 = pure vapour
presure of B. XA = mole fraction of A in liquid
phase. YA = mole fraction of A in vapour phase.
ic
Match the solutions with their characteristics.
Column I
Column II
(p) Can be separated by
(A) n-Hexane + n-hepdistillation
tane
(B) Acetone + chloro(q) Maximum boiling
form
azeotrope
(C) Acetone + aniline
(r) Cannot be separated
by distillation
(D) Ethanol + water
(s) Shows ideal behavior
87.
at
Match the van′t Hoff factor with the type of
behavior.
Column I
Column II
(A) i > 1
(p) Solution of NaCl + H2O
Match the behavior exhibited with the solutions
Column I
Column II
(A) Show ideal behavior (p) Chloroform + benzene
(q) Chloroform + Acetone
(B) Show negative
deviation from ideal
(C) Show positive
(r) Benzene + toluene
deviation from ideal
(D) Non-ideal solution
(s) Carbon tetrachloride +
chloroform
ns
Column I
(A) Molarity of the solution
(B) Molality of the solution
86.
io
have correct matching with one or more statements in
Column II.
81.
For a 5% solution of H2SO4 (ρ = 1.01 g mL–1),
match the quantities with their values.
37
9818536667
If there is dissociation of non-volatile solute
then the V.P. of solution increases
95.
Effect of adding a non-volatile solute to a solvent
is to increase its freezing point
96.
Molality is a dimensionless quantity
97.
The hard shell of an egg was dissolved in HCl
solution, and then egg was placed in concentrated
solution of NaCl. Then egg will shrink.
98.
At definite temperature, the solubility of a solute
is fixed
99.
Reverse osmosis is generally used to make
saline water fit for domestic use.
100.
On diluting the solution, its normality and
molarity changes but molality remains constant.
101.
The real solutions can exhibit ideal behaviour at
high concentrations.
102.
The mass of water present in 200 g of 10%
aqueous solution of caustic soda is 90 g.
105.
bl
104.
What is the physical state of solvent in Na2SO4 ×
10H2O(s)?.............
Identify solvent in Na2SO4 × 10H2O(s)...........
In moist air solvent is ……… .
Pu
103.
ic
FILL IN THE BLANKS
at
94.
What is the effect of temperature on the molality
of a solution?..............
107.
If (molar mass)obs = (molar mass)calc. and if
the solvent is water then predict whether the
solute is electrolytic or non-electrolytic............
Can we say that for non-electrolytic solutes
observed v.p. of solution is equal to its calculated
value?.............................
For reverse osmosis how much pressure should
be applied?..........................
M
109.
O
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106.
108.
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110.
Which type of solutes show colligative
properties, volatile or non-volatile?....................
111.
What is the sign of (DG)sol for a non-ideal
solution?...................
112.
What is the sign of (DS) for ideal solutions........
113.
A solution of CHCl3 and acetone shows ......
deviation.
114.
Among 0.1 M solutions of NaCl, CaCl2 and
Al2(SO4)3, the one with highest vapour pressure is
.........
9818536667
Solutions
39
Answer Key
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(a)
2. (c)
3. (c)
4. (d)
5. (b)
6. (a)
(b)
8. (b)
9. (d)
10. (a)
11. (c)
12. (b)
(b)
14. (a)
15. (c)
16. (a)
17. (d)
18. (a)
(b)
20. (a)
21. (b)
22. (c)
23. (a)
24. (a)
(b)
26. (c)
27. (c)
28. (b)
29. (b)
30. (c)
(c)
32. (c)
33. (a)
34. (d)
35. (c)
36. (a)
(c)
38. (d)
29. (a)
40. (b)
41. (a)
42. (c)
(a)
44. (a)
45. (c)
46. (b)
47. (c)
48. (b)
(a,b)
50. (c,d)
51. (a)
52. (c)
53. (a)
54. (c)
(a)
56. (b)
57. (c)
58. (a)
59. (d)
60. (b)
(c)
62. (c)
63. (d)
64. (b)
65. (c)
66. (a)
(b)
68. (b)
69. (d)
70. (d)
71. (d)
72. (c)
(c)
74. (b)
75. (d)
76. (a)
77. (b)
78. (a)
(b)
80. (b)
A → (s); B → (p); C → (q); D → (r)
82. A → (q); B → (p); C → (s); D → (r)
A → (p, s); B → (q, r); C → (q, r); D → (r)
84. A → (q); B → (p); C → (r); D → (s)
A → (q, r); B → (q, r); C → (p, s); D → (p, s)
86. A → (r); B → (q); C → (s); D → (p, q, s)
A → (p); B ® (r);C → (q);D → (r, s)
88. A → (q); B ® (p);C → (r, s);D → (p)
True
90. True
91. True
92. True
93. True
94. False
False
96. False
97. True
98. True
99. True
100. False
False
102. False
103. Solid
104. Na2SO4(s) 105. Air (Gas) 106. No effect
Non-electrolyte
108. No, solute may associate.
Greater than osmotic pressure. 110. Non-volatile 111. Negative
112. Positive
113. negative
0.1 M NaCl
M
O
S
1.
7.
13.
19.
25.
31.
37.
43.
49.
55.
61.
67.
73.
79.
81.
83.
85.
87.
89.
95.
101.
107.
109.
114.
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M
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9818536667