Q 1.Define Boyle’s law. How is it represented mathematically?
Ans.The volume of a given mass of a gas is inversely proportional to its pressure at constant
temperature
Mathematically V α 1/P. PV = constant
Q 2 .Define (a) Dipole-Dipole Forces (b) Avogadro law (c) Intermolecular forces .
Ans.(a) Dipole-dipole forces : The force of attraction which act between two molecules having
permanent dipoles.
(b) Avogadro Law : Equal volumes of all gases under the similar condition of temperature and
pressure contain equal number of molecules . V α n
(c) Intermolecular Forces: The forces of attractions and repulsion between interacting particles.
Q 3 .Define dispersion forces. Write characteristic features of dispersion forces.
Ans. Dispersion forces: The forces of attraction between two temporary dipoles.
Characteristics of dispersion forces:
(i) These forces are always attractive.
(ii) These forces are effective only at short distance.
(iii) Their magnitude depends on the polarisability of the particles
Q 4 .Describe Charle’s Law. In terms of Charle’s Law explain why -273
0
C is the lowest temperature?
Ans. The volume of a fixed mass of a gas is directly proportional to its absolute temperature at
constant Pressure. V α T , constant P.
At -273
0
C, volume of the gas approaches to zero i.e the gas ceases to exist.
Q5 Give one example for each of the following types of inter-particle forces .
(a) London dispersion forces
(b)Dipole-Dipole forces
(c) Hydrogen bond
(d) Ion-dipole forces
Ans. (a) noble gases.
(b) between HCl molecules.
(c) Between water molecules or HF molecules.
(d)Between NO3
-and water molecules.
Q 6 What are isochores? From the three isochores I, II, III given below, for a certain amount of ideal
Gas,What is the correct arrangement of volumes V1,V2 and V3.
Ans. Isochore is the plot beween P and T for a definite amount of a gas at a constant volume.
From different isochors at different volumes draw a line parallel to Temperature axis represent a
constant P and cutting the three isochors at T1,T
2 and T3 respectively.Fr om the graph we find T1,>T
2
>T3. Since V α T , at constant P. Thus V1 > V2 > V3.
(draw from text)
Q7. In a hospital an oxygen cylinder holds 10 L of oxygen at 200atm pressure. If a patient breathes
in 0.50ml of oxygen at 1atm with each breath, for how many breaths the cylinder will be sufficient.
(Assume that all the data is at 30
0
C.)................( 4x10
6 )
Q 8. Explain the absolute zero (in terms of volume) with the help of isobar.
Ans: At absolute zero ,volume approach to zero and below this temperature, the volume will be
negative, which is meaningless. Hence absolute zero is the lowest possible temperature .
.....................................................................................................................................................
• Stronger intermolecular forces result in higher boiling point
• Strength of London forces increases with the number of electrons in the molecule
• Boiling point of HF ,HCl, HBr and HI are 293K,189K,206K and 238K respectively
.....................................................................................................................................................
Q1.What is Boyle’s point?
Ans. The temperature at which the real gas obeys ideal gas law for an appreciable range of
pressure is called Boyle’s point.
Q2.Why liquid drops are spherical in shape?
Ans. Because of surface tension, the molecules tend to minimize the surface area and sphere has
minimum surface area.
Q3.State with expression Dalton’s law of partial pressure?
Ans. The total pressure exerted by the mixture of non reactive gases is equal to the sum of the
partial pressures of individual gases.
Ptotal = p1 + p2 + p3 +…………………
Q4.What are the two faulty assumptions of kinetic theory of gases?
Ans. i) There is no force of attraction and repulsion between the molecules of a gas.
ii) Volume of the molecules of a gas is negligibly small in comparison to the empty space
between them.
Q5. Give the units of Vander Waal’s constants a and b.
Q6. Give Vander Waal’s equation of state for real gases? What is the significance of constants a
and b in this equation?
Q7.What is the effect of temperature on surface tension and viscosity of a liquid?
Ans. Both decrease by increasing temperature.
Q8. Account for the following properties of gases on the basis of kinetic molecular theory of gases-a) high compressibility b) gases occupy whole of the volume available to them.
Ans. a) High compressibility is due to large empty space between the gas molecules.
b) Due to absence of attractive forces between the molecules, they can easily separate from
one another.
Q9. Explain the pressure and volume corrections in ideal gas equation?
Ans. At low temperature and high pressure intermolecular attractions cannot be neglected, the
observed pressure P is smaller than the ideal pressure Pi
.
Therefore, Pi = P + p = P + an
2
/V
2
As volume of gas molecules is not negligible as compared to total volume of the gas
the ideal volume Vi
is smaller than the observed volume.
Therefore, Vi
= V + v = V - nb
Q10. What is meant by compressibility factor of gases? How does its value deviate from that of an
ideal gas in case of real gases and what does it indicate?
Ans. It is the ratio of the product PV to nRT.
Z = PV/nRT. For ideal gas its value is unity. Z < 1 indicates negative deviation i.e. gas is more
compressible due predominance of attractive forces. Z > 1 indicates positive deviation i.e.
gas is less compressible due predominance of repulsive forces.
.....................................................................................................................................
Critical pressure(Pc) – it is the pressure required to liquefy the gas at critical temperature.
Critical volume( Vc) – it is the volume of one mole of the gas at T
cand Pc
........................................................................................................................................
Q1.Explain:
i)Vapour pressure increases with increase in temperature.
ii)Giycerine is more viscous than water.
Ans. i) At higher temperature inter particle attraction weakens and more number of mole cules
escape to vapour.
ii) As interparticle forces are stronger in glycerine.
Q. Derive relation between density and pressure of a gas
Q.At what temperature 128 g of SO2 confined in vessel of 5 dm
3
capacity will exhibit a pressure of
10.0 bar? Given a = 6.7 bar L
2
mol
-2
and b= 0.0564 L mol
-
Q. Calculate the pressure exerted by 8.5 g of NH3 contained in a 0.5 L vessel at 300 K. For ammonia
a = 4.0 atm L
2
mol
-2
and b = 0.036 L mol
-1
Q5. Derive ideal gas equation.
.......................................................................................................
........................................................................
...............................................
........................
...........
Ans.The volume of a given mass of a gas is inversely proportional to its pressure at constant
temperature
Mathematically V α 1/P. PV = constant
Q 2 .Define (a) Dipole-Dipole Forces (b) Avogadro law (c) Intermolecular forces .
Ans.(a) Dipole-dipole forces : The force of attraction which act between two molecules having
permanent dipoles.
(b) Avogadro Law : Equal volumes of all gases under the similar condition of temperature and
pressure contain equal number of molecules . V α n
(c) Intermolecular Forces: The forces of attractions and repulsion between interacting particles.
Q 3 .Define dispersion forces. Write characteristic features of dispersion forces.
Ans. Dispersion forces: The forces of attraction between two temporary dipoles.
Characteristics of dispersion forces:
(i) These forces are always attractive.
(ii) These forces are effective only at short distance.
(iii) Their magnitude depends on the polarisability of the particles
Q 4 .Describe Charle’s Law. In terms of Charle’s Law explain why -273
0
C is the lowest temperature?
Ans. The volume of a fixed mass of a gas is directly proportional to its absolute temperature at
constant Pressure. V α T , constant P.
At -273
0
C, volume of the gas approaches to zero i.e the gas ceases to exist.
Q5 Give one example for each of the following types of inter-particle forces .
(a) London dispersion forces
(b)Dipole-Dipole forces
(c) Hydrogen bond
(d) Ion-dipole forces
Ans. (a) noble gases.
(b) between HCl molecules.
(c) Between water molecules or HF molecules.
(d)Between NO3
-and water molecules.
Q 6 What are isochores? From the three isochores I, II, III given below, for a certain amount of ideal
Gas,What is the correct arrangement of volumes V1,V2 and V3.
Ans. Isochore is the plot beween P and T for a definite amount of a gas at a constant volume.
From different isochors at different volumes draw a line parallel to Temperature axis represent a
constant P and cutting the three isochors at T1,T
2 and T3 respectively.Fr om the graph we find T1,>T
2
>T3. Since V α T , at constant P. Thus V1 > V2 > V3.
(draw from text)
Q7. In a hospital an oxygen cylinder holds 10 L of oxygen at 200atm pressure. If a patient breathes
in 0.50ml of oxygen at 1atm with each breath, for how many breaths the cylinder will be sufficient.
(Assume that all the data is at 30
0
C.)................( 4x10
6 )
Q 8. Explain the absolute zero (in terms of volume) with the help of isobar.
Ans: At absolute zero ,volume approach to zero and below this temperature, the volume will be
negative, which is meaningless. Hence absolute zero is the lowest possible temperature .
.....................................................................................................................................................
• Stronger intermolecular forces result in higher boiling point
• Strength of London forces increases with the number of electrons in the molecule
• Boiling point of HF ,HCl, HBr and HI are 293K,189K,206K and 238K respectively
.....................................................................................................................................................
Q1.What is Boyle’s point?
Ans. The temperature at which the real gas obeys ideal gas law for an appreciable range of
pressure is called Boyle’s point.
Q2.Why liquid drops are spherical in shape?
Ans. Because of surface tension, the molecules tend to minimize the surface area and sphere has
minimum surface area.
Q3.State with expression Dalton’s law of partial pressure?
Ans. The total pressure exerted by the mixture of non reactive gases is equal to the sum of the
partial pressures of individual gases.
Ptotal = p1 + p2 + p3 +…………………
Q4.What are the two faulty assumptions of kinetic theory of gases?
Ans. i) There is no force of attraction and repulsion between the molecules of a gas.
ii) Volume of the molecules of a gas is negligibly small in comparison to the empty space
between them.
Q5. Give the units of Vander Waal’s constants a and b.
Q6. Give Vander Waal’s equation of state for real gases? What is the significance of constants a
and b in this equation?
Q7.What is the effect of temperature on surface tension and viscosity of a liquid?
Ans. Both decrease by increasing temperature.
Q8. Account for the following properties of gases on the basis of kinetic molecular theory of gases-a) high compressibility b) gases occupy whole of the volume available to them.
Ans. a) High compressibility is due to large empty space between the gas molecules.
b) Due to absence of attractive forces between the molecules, they can easily separate from
one another.
Q9. Explain the pressure and volume corrections in ideal gas equation?
Ans. At low temperature and high pressure intermolecular attractions cannot be neglected, the
observed pressure P is smaller than the ideal pressure Pi
.
Therefore, Pi = P + p = P + an
2
/V
2
As volume of gas molecules is not negligible as compared to total volume of the gas
the ideal volume Vi
is smaller than the observed volume.
Therefore, Vi
= V + v = V - nb
Q10. What is meant by compressibility factor of gases? How does its value deviate from that of an
ideal gas in case of real gases and what does it indicate?
Ans. It is the ratio of the product PV to nRT.
Z = PV/nRT. For ideal gas its value is unity. Z < 1 indicates negative deviation i.e. gas is more
compressible due predominance of attractive forces. Z > 1 indicates positive deviation i.e.
gas is less compressible due predominance of repulsive forces.
.....................................................................................................................................
Critical pressure(Pc) – it is the pressure required to liquefy the gas at critical temperature.
Critical volume( Vc) – it is the volume of one mole of the gas at T
cand Pc
........................................................................................................................................
Q1.Explain:
i)Vapour pressure increases with increase in temperature.
ii)Giycerine is more viscous than water.
Ans. i) At higher temperature inter particle attraction weakens and more number of mole cules
escape to vapour.
ii) As interparticle forces are stronger in glycerine.
Q. Derive relation between density and pressure of a gas
Q.At what temperature 128 g of SO2 confined in vessel of 5 dm
3
capacity will exhibit a pressure of
10.0 bar? Given a = 6.7 bar L
2
mol
-2
and b= 0.0564 L mol
-
Q. Calculate the pressure exerted by 8.5 g of NH3 contained in a 0.5 L vessel at 300 K. For ammonia
a = 4.0 atm L
2
mol
-2
and b = 0.036 L mol
-1
Q5. Derive ideal gas equation.
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...........
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