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# Byjus's Physical Chemistry MCQs MBBS Notes | EduRev

## MBBS : Byjus's Physical Chemistry MCQs MBBS Notes | EduRev

``` Page 1

Liquid State
Page 2

Liquid State
• MSc., PhD, NET, JRF
• 18 year experience of IIT JEE in Organic Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota and Bansal Classes, Kota
PIYUSH MAHESHWARI
• BE (Hons.)
• 11 year experience of IIT JEE in InorganicChemistry
• Author of 'Super Problems in Inorganic Chemistry',
• Ex. HOD Bansal Classes, Kota
• Ex. Senior Faculty of Vibrant Academy, Kota and Allen Career Institute, Kota
BRIJESH JINDAL
• BTech Jaipur MNIT
• 11 year experience of IIT JEE in Physical Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota, Allen Career Institute, Kota and Bansal
Classes, Kota
Page 3

Liquid State
• MSc., PhD, NET, JRF
• 18 year experience of IIT JEE in Organic Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota and Bansal Classes, Kota
PIYUSH MAHESHWARI
• BE (Hons.)
• 11 year experience of IIT JEE in InorganicChemistry
• Author of 'Super Problems in Inorganic Chemistry',
• Ex. HOD Bansal Classes, Kota
• Ex. Senior Faculty of Vibrant Academy, Kota and Allen Career Institute, Kota
BRIJESH JINDAL
• BTech Jaipur MNIT
• 11 year experience of IIT JEE in Physical Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota, Allen Career Institute, Kota and Bansal
Classes, Kota
LIQUID STATE
Page # 1
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
EXERCISE-1 (Subjective Questions)
INTERCONVERSIONS OF CONCENTRATION TERMS
Q.1 Calculate the mole ratio of C
2
H
5
OH and CH
3
OH in aqueous solution if molality of C
2
H
5
OH is 40/9 and
mole fraction of CH
3
OH is 0.1 in solution.
Q.2 Molarity of aqueous NaOH solution will be, if mole fraction of NaOH in the solution is 0.5.
[Given : Density of pure NaOH = 4 gm/ml]
Q.3 The density of toluene (C
7
H
8
) is 0.8 g/ml and density of thiophene (C
4
H
4
S) is 1 g/ml. A solution is made
by dissolving 8.4 g of thiophene in 250 ml of toluene calculate
(a) mole fraction of thiophene in the solution.
(b) molality of thiophene in the solution
(c) Assuming that volume of solute and solvent are additive, what is the molarity of thiophene in the
solution.
Q.4 Commercial aqueous nitric acid has density 1.4 g/ml and molarity 15 M. Calculate the percentage of
HNO
3
by mass in the solution.
Q.5 Calculate molality of 2M aqueous solution of NaOH having density 1.2 g/ml.
RAOULT’S LAW & DALTON'S LAW IN BINARY LIQUID SOLUTION
Q.6 The vapour pressure of ethanol and methanol are 44.5 mm Hg and 88.7 mm Hg respectively. An ideal
solution is prepared at the same temperature by mixing 60 g of ethanol with 40 g of methanol. Calculate
total vapour pressure of the solution.
Q.7 Calculate the mole fraction of toluene in the vapour phase which is in equilibrium with a solution of
benzene and toluene having a mole fraction of toluene 0.50. The vapour pressure of pure benzene is
119 torr; that of toluene is 37 torr at the same temperature.
Q.8 What is the composition of the vapour which is in equilibrium at 30°C with a benzene-toluene solution
with a mole fraction of benzene of 0.40? With a mole fraction of benzene of 0.60?
?
b
P =119 torr and
?
t
P = 37 torr
Q.9 At 90°C, the vapour pressure of toluene is 400 torr and that of s-xylene is 150 torr. What is the composition
of the liquid mixture that boils at 90°C, when the pressure is 0.50 atm? What is the composition of
vapour produced?
Q.10 Two liquids A and B form an ideal solution at temperature T. When the total vapour pressure above the
solution is 400 torr, the mole fraction of A in the vapour phase is 0.40 and in the liquid phase 0.75. What
are the vapour pressure of pure A and pure B at temperature T?
Q.11 Benzene and toluene form two ideal solution A and B at 313 K. Solution A (total pressure P
A
) contains
equal mole of toluene and benzene. Solution B contains equal masses of both (total pressure P
B
). The
vapour pressure of benzene and toluene are 160 and 60 mm Hg respectively at 313 K. Calculate the
value of P
A
/P
B
.
Page 4

Liquid State
• MSc., PhD, NET, JRF
• 18 year experience of IIT JEE in Organic Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota and Bansal Classes, Kota
PIYUSH MAHESHWARI
• BE (Hons.)
• 11 year experience of IIT JEE in InorganicChemistry
• Author of 'Super Problems in Inorganic Chemistry',
• Ex. HOD Bansal Classes, Kota
• Ex. Senior Faculty of Vibrant Academy, Kota and Allen Career Institute, Kota
BRIJESH JINDAL
• BTech Jaipur MNIT
• 11 year experience of IIT JEE in Physical Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota, Allen Career Institute, Kota and Bansal
Classes, Kota
LIQUID STATE
Page # 1
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
EXERCISE-1 (Subjective Questions)
INTERCONVERSIONS OF CONCENTRATION TERMS
Q.1 Calculate the mole ratio of C
2
H
5
OH and CH
3
OH in aqueous solution if molality of C
2
H
5
OH is 40/9 and
mole fraction of CH
3
OH is 0.1 in solution.
Q.2 Molarity of aqueous NaOH solution will be, if mole fraction of NaOH in the solution is 0.5.
[Given : Density of pure NaOH = 4 gm/ml]
Q.3 The density of toluene (C
7
H
8
) is 0.8 g/ml and density of thiophene (C
4
H
4
S) is 1 g/ml. A solution is made
by dissolving 8.4 g of thiophene in 250 ml of toluene calculate
(a) mole fraction of thiophene in the solution.
(b) molality of thiophene in the solution
(c) Assuming that volume of solute and solvent are additive, what is the molarity of thiophene in the
solution.
Q.4 Commercial aqueous nitric acid has density 1.4 g/ml and molarity 15 M. Calculate the percentage of
HNO
3
by mass in the solution.
Q.5 Calculate molality of 2M aqueous solution of NaOH having density 1.2 g/ml.
RAOULT’S LAW & DALTON'S LAW IN BINARY LIQUID SOLUTION
Q.6 The vapour pressure of ethanol and methanol are 44.5 mm Hg and 88.7 mm Hg respectively. An ideal
solution is prepared at the same temperature by mixing 60 g of ethanol with 40 g of methanol. Calculate
total vapour pressure of the solution.
Q.7 Calculate the mole fraction of toluene in the vapour phase which is in equilibrium with a solution of
benzene and toluene having a mole fraction of toluene 0.50. The vapour pressure of pure benzene is
119 torr; that of toluene is 37 torr at the same temperature.
Q.8 What is the composition of the vapour which is in equilibrium at 30°C with a benzene-toluene solution
with a mole fraction of benzene of 0.40? With a mole fraction of benzene of 0.60?
?
b
P =119 torr and
?
t
P = 37 torr
Q.9 At 90°C, the vapour pressure of toluene is 400 torr and that of s-xylene is 150 torr. What is the composition
of the liquid mixture that boils at 90°C, when the pressure is 0.50 atm? What is the composition of
vapour produced?
Q.10 Two liquids A and B form an ideal solution at temperature T. When the total vapour pressure above the
solution is 400 torr, the mole fraction of A in the vapour phase is 0.40 and in the liquid phase 0.75. What
are the vapour pressure of pure A and pure B at temperature T?
Q.11 Benzene and toluene form two ideal solution A and B at 313 K. Solution A (total pressure P
A
) contains
equal mole of toluene and benzene. Solution B contains equal masses of both (total pressure P
B
). The
vapour pressure of benzene and toluene are 160 and 60 mm Hg respectively at 313 K. Calculate the
value of P
A
/P
B
.
LIQUID STATE
Page # 2
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
RAOULT’S LAW & VAPOUR PRESSURE LOWERING
Q.12 Calculate the mass of propylene glycol(C
3
H
8
O
2
) that must be added to 0.54 Kg of water to reduce its
vapour pressure by 3 torr at 40°C.
[Given : Vapour pressure of water at 40°C is 25 torr]
Q.13 At 25°C, the vapour pressure of methyl alcohol is 96.0 torr. What is the mole fraction of CH
3
OH in a
solution in which the (partial) vapor pressure of CH
3
OH is 23.0 torr at 25°C?
Q.14 The vapour pressure of pure liquid solvent A is 0.80 atm. When a nonvolatile substance B is added to the
solvent its vapour pressure drops to 0.60 atm. What is the mole fraction of component B in the solution?
Q.15 The vapour pressure of pure water at 26°C is 25.21 torr. What is the vapour pressure of a solution
which contains 20.0 g glucose, C
6
H
12
O
6
, in 70 g water?
Q.16 The vapour pressure of pure water at 25°C is 23.76 torr. The vapour pressure of a solution containing
5.40 g of a nonvolatile substance in 90.0 g water is 23.32 torr. Compute the molecular weight of the
solute.
Q.17 Calculate the relative lowering in vapour pressure if 100 g of a nonvolatile solute (mol.wt.100) are
dissolved in 432 g water.
Q.18 What weight of the non-volatile solute, urea needs to be dissolved in 100 g of water, in order to decrease
the vapour pressure of water by 25%? What will be the molality of the solution?
Q.19 The vapour pressure of an aqueous solution of glucose is 750 mm Hg at 373 K. Calculate molality and
mole fraction of  solute.
Q.20 The vapour pressure of pure benzene at 25° C is 639.7 mm of Hg and the vapour pressure of a solution
of a solute in C
6
H
6
at the same temperature is 631.7 mm of Hg. Calculate molality of solution.
Q.21 The vapour pressure of pure benzene at a certain temperature is 640 mm of Hg. A nonvolatile nonelectrolyte
solid weighing 2.175 g is added to 39.0 of benzene. The vapour pressure of the solution is 600 mm of
Hg. What is molecular weight of solid substance?
Q.22 The vapour pressure of water is 17.54 mm  Hg at 293K. Calculate vapour pressure of 0.5 molal solution
of a solute in it.
BOILING POINT ELEVATION AND FREEZING POINT DEPRESSION
Q.23 When 10.6 g of a nonvolatile substance is dissolved in 740 g of ether, its boiling point is raised 0.284°C.
What is the molecular weight of the substance? Molal boiling point constant for ether is 2.11°C·kg/mol.
Q.24 A solution containing 3.24 g of a nonvolatile nonelectrolyte and 200 g of water boils at 100.130°C at
1atm. What is the molecular weight of the solute? (K
b
for water 0.513°C/m)
Q.25 The molecular weight of an organic compound is 58.0 g/mol. Compute the boiling point of a solution
containing 24.0 g of the solute and 600 g of water, when the barometric pressure is such that pure water
boils at 99.725°C.(K
b
for water 0.513°C/m)
Q.26 An aqueous solution of a nonvolatile solute boils at 100.17°C. At what temperature will this solution
freeze? [K
b

for water 0.52°C/m

]
Page 5

Liquid State
• MSc., PhD, NET, JRF
• 18 year experience of IIT JEE in Organic Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota and Bansal Classes, Kota
PIYUSH MAHESHWARI
• BE (Hons.)
• 11 year experience of IIT JEE in InorganicChemistry
• Author of 'Super Problems in Inorganic Chemistry',
• Ex. HOD Bansal Classes, Kota
• Ex. Senior Faculty of Vibrant Academy, Kota and Allen Career Institute, Kota
BRIJESH JINDAL
• BTech Jaipur MNIT
• 11 year experience of IIT JEE in Physical Chemistry
• Ex. Senior Faculty of Vibrant Academy, Kota, Allen Career Institute, Kota and Bansal
Classes, Kota
LIQUID STATE
Page # 1
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
EXERCISE-1 (Subjective Questions)
INTERCONVERSIONS OF CONCENTRATION TERMS
Q.1 Calculate the mole ratio of C
2
H
5
OH and CH
3
OH in aqueous solution if molality of C
2
H
5
OH is 40/9 and
mole fraction of CH
3
OH is 0.1 in solution.
Q.2 Molarity of aqueous NaOH solution will be, if mole fraction of NaOH in the solution is 0.5.
[Given : Density of pure NaOH = 4 gm/ml]
Q.3 The density of toluene (C
7
H
8
) is 0.8 g/ml and density of thiophene (C
4
H
4
S) is 1 g/ml. A solution is made
by dissolving 8.4 g of thiophene in 250 ml of toluene calculate
(a) mole fraction of thiophene in the solution.
(b) molality of thiophene in the solution
(c) Assuming that volume of solute and solvent are additive, what is the molarity of thiophene in the
solution.
Q.4 Commercial aqueous nitric acid has density 1.4 g/ml and molarity 15 M. Calculate the percentage of
HNO
3
by mass in the solution.
Q.5 Calculate molality of 2M aqueous solution of NaOH having density 1.2 g/ml.
RAOULT’S LAW & DALTON'S LAW IN BINARY LIQUID SOLUTION
Q.6 The vapour pressure of ethanol and methanol are 44.5 mm Hg and 88.7 mm Hg respectively. An ideal
solution is prepared at the same temperature by mixing 60 g of ethanol with 40 g of methanol. Calculate
total vapour pressure of the solution.
Q.7 Calculate the mole fraction of toluene in the vapour phase which is in equilibrium with a solution of
benzene and toluene having a mole fraction of toluene 0.50. The vapour pressure of pure benzene is
119 torr; that of toluene is 37 torr at the same temperature.
Q.8 What is the composition of the vapour which is in equilibrium at 30°C with a benzene-toluene solution
with a mole fraction of benzene of 0.40? With a mole fraction of benzene of 0.60?
?
b
P =119 torr and
?
t
P = 37 torr
Q.9 At 90°C, the vapour pressure of toluene is 400 torr and that of s-xylene is 150 torr. What is the composition
of the liquid mixture that boils at 90°C, when the pressure is 0.50 atm? What is the composition of
vapour produced?
Q.10 Two liquids A and B form an ideal solution at temperature T. When the total vapour pressure above the
solution is 400 torr, the mole fraction of A in the vapour phase is 0.40 and in the liquid phase 0.75. What
are the vapour pressure of pure A and pure B at temperature T?
Q.11 Benzene and toluene form two ideal solution A and B at 313 K. Solution A (total pressure P
A
) contains
equal mole of toluene and benzene. Solution B contains equal masses of both (total pressure P
B
). The
vapour pressure of benzene and toluene are 160 and 60 mm Hg respectively at 313 K. Calculate the
value of P
A
/P
B
.
LIQUID STATE
Page # 2
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
ChemistryExperts
RAOULT’S LAW & VAPOUR PRESSURE LOWERING
Q.12 Calculate the mass of propylene glycol(C
3
H
8
O
2
) that must be added to 0.54 Kg of water to reduce its
vapour pressure by 3 torr at 40°C.
[Given : Vapour pressure of water at 40°C is 25 torr]
Q.13 At 25°C, the vapour pressure of methyl alcohol is 96.0 torr. What is the mole fraction of CH
3
OH in a
solution in which the (partial) vapor pressure of CH
3
OH is 23.0 torr at 25°C?
Q.14 The vapour pressure of pure liquid solvent A is 0.80 atm. When a nonvolatile substance B is added to the
solvent its vapour pressure drops to 0.60 atm. What is the mole fraction of component B in the solution?
Q.15 The vapour pressure of pure water at 26°C is 25.21 torr. What is the vapour pressure of a solution
which contains 20.0 g glucose, C
6
H
12
O
6
, in 70 g water?
Q.16 The vapour pressure of pure water at 25°C is 23.76 torr. The vapour pressure of a solution containing
5.40 g of a nonvolatile substance in 90.0 g water is 23.32 torr. Compute the molecular weight of the
solute.
Q.17 Calculate the relative lowering in vapour pressure if 100 g of a nonvolatile solute (mol.wt.100) are
dissolved in 432 g water.
Q.18 What weight of the non-volatile solute, urea needs to be dissolved in 100 g of water, in order to decrease
the vapour pressure of water by 25%? What will be the molality of the solution?
Q.19 The vapour pressure of an aqueous solution of glucose is 750 mm Hg at 373 K. Calculate molality and
mole fraction of  solute.
Q.20 The vapour pressure of pure benzene at 25° C is 639.7 mm of Hg and the vapour pressure of a solution
of a solute in C
6
H
6
at the same temperature is 631.7 mm of Hg. Calculate molality of solution.
Q.21 The vapour pressure of pure benzene at a certain temperature is 640 mm of Hg. A nonvolatile nonelectrolyte
solid weighing 2.175 g is added to 39.0 of benzene. The vapour pressure of the solution is 600 mm of
Hg. What is molecular weight of solid substance?
Q.22 The vapour pressure of water is 17.54 mm  Hg at 293K. Calculate vapour pressure of 0.5 molal solution
of a solute in it.
BOILING POINT ELEVATION AND FREEZING POINT DEPRESSION
Q.23 When 10.6 g of a nonvolatile substance is dissolved in 740 g of ether, its boiling point is raised 0.284°C.
What is the molecular weight of the substance? Molal boiling point constant for ether is 2.11°C·kg/mol.
Q.24 A solution containing 3.24 g of a nonvolatile nonelectrolyte and 200 g of water boils at 100.130°C at
1atm. What is the molecular weight of the solute? (K
b
for water 0.513°C/m)
Q.25 The molecular weight of an organic compound is 58.0 g/mol. Compute the boiling point of a solution
containing 24.0 g of the solute and 600 g of water, when the barometric pressure is such that pure water
boils at 99.725°C.(K
b
for water 0.513°C/m)
Q.26 An aqueous solution of a nonvolatile solute boils at 100.17°C. At what temperature will this solution
freeze? [K
b

for water 0.52°C/m

]
LIQUID STATE
Page # 3
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Q.27 Pure benzene freeze at 5.45°C. A solution containing 7.24 g of C
2
H
2
Cl
4
in 115.3 g of benzene was
observed to freeze at 3.55°C. What is the molal freezing point constant of benzene?
Q.28 A solution containing 6.35 g of a nonelectrolyte dissolved in 500 g of water freezes at – 0.465°C.
Determine the molecular weight of the solute.[K
f

for water 1.86°C/m

]
Q.29 The freezing point of a solution containing 2.40 g of a compound in 60.0 g of benzene is 0.10°C lower
than that of pure benzene. What is the molecular weight of the compound? (K
f
is 5.12°C/m for benzene)
Q.30 The elements X and Y form compounds having molecular formula XY
2
and XY
4
. When dissolved in 20 gm
of benzene, 1 gm XY
2
lowers the freezing point by 2.3°, whereas 1 gm of XY
4
lowers the freezing point by
1.3°C. The molal depression constant for benzene is 5.1. Calculate the atomic masses of X and Y .
Q.31 Calculate the molal elevation constant, K
b
for water and the boiling point of 0.1 molal urea solution.
Latent heat of vaporisation of water is 9.72 kcal mol
–1
at 373.15 K.
Q.32 A solution of  0.643 g of an  organic compound in 50ml of benzene (density ; 0.879 g/ml) lowers its
freezing point from 5.51°C to 5.03°C. If K
f
for benzene is 5.12 K, calculate the molecular weight of the
compound.
Q.33 What is the freezing point of an aqueous solution that boils at 104°C ?
[Given : K
f
= 1.86 °C/m, K
b
= 0.51 °C/m]
Q.34 How many gram of ethylene glycol (C
2
H
6
O
2
) must be added to 0.4 Kg of water to produce a solution
that freezes at –5°C ?
Q.35 Calculate freezing and boiling points of each of following solutions :
(a) 0.25 m glucose in ethanol.
(b) 20 g of decane in 50g CHCl
3
.
(c) 4 g NaOH in 200g of water.
(d) 0.45 mol ethylene glycol (C
2
H
6
O
2
) & 0.15 mol KBr in 200g H
2
O.
Given :
S.No. Solvent Normal Boiling K
b
Normal freezing K
f
Point(°C) (°C/m) Point(°C) (°C/m)
1. Water 100 0.51 0 1.86
(H
2
O)
2. Chloroform 61.2 3.63 – 63.5 4.68
(CHCl
3
)
3. Ethanol 78.4 1.22 – 114.6 2
(C
2
H
5
OH)
Q.36 The cryoscopic constant for acetic acid is 3.6 K kg/mol. A solution of 1 g of a hydrocarbon in 100 g of
acetic acid  freezes at 16.14°C instead of the usual 16.60°C. The hydrocarbon contains 92.3% carbon.
What is the molecular formula?
Q.37 Match the boiling point with K
b
for x, y and z, if molecular weight of x, y and z are same.
b.pt. K
b
x 100 0.68
y 27 0.53
z 253 0.98
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