CHAPTER PRACTICE PROBLEMS
FIITJEE
CHEMISTRY
Gaseous State
Name : ______________________________________ Batch :
Date :
Ideal Gas Equation:
3
3
1. The densities of an unknown gas and O2 were found 0.2579 kg/m and 0.2749 kg/m at the same P and T.
Calculate molecular mass of unknown gas.
Ans: [M = 30.02]
2. Air is pumped into an automobile tyre tube upto a pressure of 200 k Pa at 20°C. As the temperature rises to
40°C, the tube expand by 20%. Calculate pressure in tube at 40°C. Assume ideal nature.
3. 0.75 mole solid A4 and 2 moles of O2 are heated in a sealed tube to react completely and producing one mole
of the compound. If product formed is also in gaseous state. Predict ratio of final pressure at 600 K to initial
pressure at 300 K.
4. Which of the following curves is not true representation of Boyle’s Law?
(A)
(B)
(C)
(D)
PV
P
-log P
PV
V
1/V
P
2
log PV
5. 34.05 ml of phosphorus vapour weighs 0.0625 g at 546°C and 1 bar pressure. What is the molar mass of
phosphorus?
6. What will be the temperature difference needed in a hot air balloon to lift 1.0 kg weight. Assume that the
3
0
volume of balloon is 100 m , the temperature of atmosphere is 25 C and pressure is 1.0 atmosphere.
Average molar mass of air is 29 amu. [3]
o
7. A gas cylinder contains 370 g oxygen gas at 30 atm pressure and 25 C. What mass of oxygen would escape
o
if first the cylinders were heated at 75 C and then the valve were held open until the gas pressure was 1.00
o
atm the temp. being maintained at 75 C
(A) 359 g
(B) 400 g
(C) 200 g
(D) 300 g
Ans: [A]
8. Argon gas liberated from crushed meteorites does not have the same isotopic composition at atmospheric
o
argon. The gas density of a particular sample of meteoritic Ar was found to be 1.481 g / l at 27 C and 740
torr. The Average atomic weight of Ar is
(A) 37.5 g / l
(B) 47.5 g / l
(C) 40 g / l
(D) 44 g / l
9. A gas cylinder containing cooking gas can withstand of 14.9 atm. The pressure gauge of cylinder indicates 12
0
atm at 27 C. Due to sudden fire in the building, its temperature starts rising. At what temperature the cylinder
will explode?
(A) 1000 K
(B) 372.5 K
(C) 500.3 K
(D) none of these
Ans: [B]
0
10. The volume occupied by 5 g of acetylene gas at 50 C and 740 mm pressure is
(A) 2.23 L
(B) 5.24 L
(C) 3.05 L
11. At which of the four conditions, the density of nitrogen will be maximum?
(A) STP
(B) 273 K and 2 atm
(C) 546 K and 1 atm
(D) none of these
Ans: [B]
(D) 546 K and 2 atm
12. A sample of gaseous arsine ( AsH3 )in a 500 ml flask at 300 torr and 223 K is heated to 473 K, at which AsH3
decomposes to solid arsenic and H2 gas. The flask is then cooled to 273 K, at which pressure in flask 508
torr. Calculate % of AsH3 decomposed.
CHAPTER PRACTICE PROBLEMS
CHEMISTRY
FIITJEE
13. 4 litre C2H4 ( g ) burns in oxygen at 27°C and 1 atm pressure to produce CO2 (g ) and H2O(g). calculate the
volume of CO2 formed at
(A) 27°C and 1 atm
(B) 127°C and 1atm
(C) 27°C and 2 atm
0
0
14. A bottle is heated with its mouth open from 15 C to 100 C. What fraction of air originally contained in the
vessel is expelled?
[23.5%]
5
15. A balloon filled with helium rises to a certain height at which it gets fully inflated to a volume of 1 × 10 litres. If
—3
at this temperature and atmospheric pressure is 268 K and 2 × 10 atm respectively, what weight of helium
will be required to fully inflate the balloon?
[36.36 g]
5
16. The density of the vapour of a substance at 373 K and 1.013 × 10 Pa is 2.55 g/lit. Calculate its molecular
weight.
10
[2.68 × 10 ]
17. A 10-cm column of air is trapped by an 8-cm long column of Hg in a capillary tube horizontally fixed as shown
in the figure at 1 atm pressure. Calculate the length of air column when the tube is fixed.
(A) vertically with open end up
(B) vertically with open end down
0
(C) at 45 from horizontal with the open end up
10 cm
8 cm
[(a) 9.04 cm, (b) 11.17 cm, (c) 9.30 cm(Hg)]
Real Gas
18. Using van der Waal’s equation of state, calculate pressure developed by 100 g of CO2 contained in a volume
0
of 5.0 litre at 40 C. Also compare this value with that calculated using ideal gas law and determine the
2
–1
2
-1
percentage deviation from ideality. A = 3.6 atm L mol , b = 44 cm mol . [P = 11.16 atm, percentage
deviation = 4.33%]
2
19. An equation of state for a non-ideal gas can be written as; PVm = A + BP + CP ; where vm is the molar volume
-2
–5
and P is the gas pressure in atmosphere. B = -2.879 × v10 and c = 14.98 × 10 in litre atmosphere unit.
Under the experimental condition, determine the pressure at which PV –P curve will attain minimum. [96 atm]
20. The van der Waals’ constant ‘a’ is a correction factor to the ideal gas law for intermolecular force of
2
-1
attractions within the substance. Match the following values of ‘a’ (L atm mol ): 0.2107, 5.464, 18.00 and
24.06 with gases benzene, toluene, Ne and Steam.
21. The van der Waals’ constant ‘b’ is a correction factor to the ideal gas law for the intrinsic volume of the
-1
molecule. Match the following values of ‘b’ (L mol ): 0.017, 0.0305, 0.1154 and 0.1463, with the gases:
toluene, benzene, Ne and steam.
22. Calculate pressure exerted by 22.0 g of CO2 in 0.5 L bulb at 300 K assuming it to be real gas with a = 363
2
—2
kPaL mol and b = 42.67 cc/mol. [22.06 atm]
23. Molar volume of He at 10.1325 Mpa and 273 K is 0.011075 times its molar volume at 101.325 kPa. Calculate
radius of He atom assuming negligible ‘a’. [134 pm]
24. Using van der Waal’s equation of state, calculate the pressure correction factor for two moles of a gas
-1
confined in a four litre flask that exert a pressure of 11 atmosphere at 300 K. b = 0.05 L mol [1.615 bar]
25. One mole of a monoatomic gas confined in a 22.5 litre flask at 273 K exert a pressure of 0.98 atm, whereas
expected pressure was 1.0 atm has the gas behaved ideally. Determine the van der Waal’s constants ‘a’ and
2
-2
2
‘b’ and Boyle’s temperature (TB). [10.12 atm L mol , 114 cm /mol & 1083.12 K]
26. The van der Waal’s constant ‘b’ of a gas is 4.42 centilitre/mol. How near can the centres of the two molecules
approach each other? [327.2 pm]
CHAPTER PRACTICE PROBLEMS
FIITJEE
CHEMISTRY
27. For carbon dioxide, critical density is 0.45 g/cc and its TC = 300 K. Determine
2
-2
its van der Waal’s constants. [2.7 atm L mol ]
0
28. The Virial equation for ethane gas is given by PV = RT + BP. At 0 C, B = - 0.1814 L/mol. Calculate volume of
2
-2
one mole of ethane at 10 atm, and ‘a’. [Z = 0.918, a = 3.77 atm L mol ]
29. What factors influence the magnitude of the temp. drop on expansion of a pure real gas into a vacuum?
(A) The intermolecular forces
(B) heat capacity
(C) Kinetic energy of molecules
(D) force of repulsion
30. Why the value of ‘a’ is larger for NH3 but that ‘b’ is larger for N2
(A) H - bonding in ammonia ‘b’ is lower because H – atoms of NH3 take up practically no Volume
(B) H – bonding in ammonia ‘b’ is lower because N – atom of NH3 take up practically no volume
1. Size of N2 is much more than NH3
(D) Size of NH3is much more than N2
31. The temperature at which 3 moles of SO2 will occupy a volume of 10 litres at a pressure of 15 atm.
2
—2
—1
(a = 6.71 atm lit mole ), (b = 0.0564 lit mole )
O
O
(A) 351 K
(B) 430 K
(C) 351 C
(D) 430 C
Ans: [C]
32. Calculate the average volume available to a molecule in a sample of N2 at NTP. Also report the average
distance between two neighbouring molecules if a nitrogen molecule is assumed to be spherical, comment on
-8
the result if the radius of one N2 molecule is 2 × 10 cm.
33. Calculate the compressibility factor for SO2 if one mole of it occupies 0.35 litre at 300 K and 50 atm pressure,
comment on the result.
34. Using van der Waals’ equation of state, find pressure at which the PV vs P curve acquires minima for 1.0
0
2
-2
3
-1
mole of oxygen gas at 0 C. a = 1.36 L atm mol , and b= 32 cm mol [165.5 atm]
35. Match the following :
List I (gas)
A
H2
1
SO2
2
.
B
.
.
C
List II (b in Lt / mol)
0.0478
0.0723
.
NH3
3
.
0.027
.
36. Match the following :
Column - I
Column - II
0
A
NH3 gas at 0 C has compressibility factor
P
equal to 1
B
H2 gas has compressibility factor
Q
less than 1
C
A gas at high temperature and low pressure has compressibility
factor
R
Zero
D
Generally the compressibility factor for a gas can’t be
S
Greater than 1
Kinetic Gas Equation & Critical Constants
2
–1
37. 6.0 g of He having average velocity 4 × 10 ms is mixed with 12.0 g of Ne
velocity. What is the average kinetic energy per mole in the mixture? [807.84 J]
20
having the same average
o
38. At what temp. will hydrogen molecules have the same r.m.s. speed as nitrogen molecule have at 35 C
o
o
(A) 22 K
(B) 220 K
(C) 35 C
(D) 135 C
CHAPTER PRACTICE PROBLEMS
FIITJEE
CHEMISTRY
0
39. Calculate the average kinetic energy per mole of CO2 gas at 27 C in different units.
[3.74 × 10
10
ergs, 3742 joules, 894 calories]
40. The critical temperature and pressure of CO2 gas are 304.2 K and 72.9 atm respectively. Calculate the radius
of CO2 molecule assuming it to behave van der Wall’s gas.
[1.62 × 10
—8
cm]
41. Calculate the temperatures at which the molecules of the first two members of the homologous seris CnH2n+2
will have the same RMS speed as CO2 gas has 770 K.
[280 K, 525 K]
COMPREHENSION – I
The behaviour of gases has been expressed in terms of various gas laws obtained experimentally i.e., Boyle’s
law, Charles’ law, Pressure – temperature law, Dalton’s law of partial pressure, Graham’s law of diffusion and
1
Avogadro’s hypothesis. Later on Maxwell derived kinetic equation PV = mnu 2 , theoretically by assuming the
3
concept of molecules and their motion.
The term u represents root mean square speed of molecule.
⎛ δP ⎞ ⎛ δV ⎞ ⎛ δV ⎞
42. For one mole of an ideal gas ⎜
⎟ .⎜
⎟ .⎜
⎟ is equal to :
⎝ δT ⎠ V ⎝ δT ⎠ P ⎝ δP ⎠ T
(A)
− R2
(B)
P2
R2
(C) +1
P2
(D) -1
43. The intercept of plots of log V vs log T curves at constant pressure P for 1 mole gas will be:
P
R
−P
−R
(A) log
(B) log
(C) log
(D) log
R
P
R
P
O
44. The average kinetic energy of 1.6 g CH4 molecules at 27 C is :
-15
-15
-15
(A) 6.21 × 10 erg
(B) 6.21 × 10 joule
(C) 6.21 × 10 calorie
(D) None of these
Graham’s Law
45. Calculate relative rate of diffusion for
-3
235
UF6 and
238
UF6
3
46. A vessel of volume 8.0 × 10 m contains ideal gas at 300 K and 200 k Pa. The gas is allowed to leak till the
pressure falls to 125 k Pa. Calculate the mole of gas leaked out if temperature remains constant.
47. What percent of a sample of nitrogen must be allowed to escape if its temp. pressure and volume are to be
o
o
changed from 220 C, 3.00 atm and 1.65 L to 110 C, 0.7 atm and 1.00 L respectively?
(A) 81.8%
(B) 18.2%
(C) 20%
(D) 80%
48. Two gases A and B having molecular weight 60 and 45 respectively are enclosed in a vessel. The weight of
A is 0.5 g and that of B is 0.2 g. The total pressure of the mixture is 750 mm. The pressure of A is
(A) 260 mm
(B) 489.5 mm
(C) 300 mm
(D) none of these
Ans: [B]
49. A gas mixture containing 5% by mass of butane and 95% by mass of Ar (40) is to be prepared by allowing
0
gaseous butane to fill an evacuated 40 L cylinder at 1.0 atm and 27 C. Calculate mass of Ar that gives the
desired composition and total pressure of the final mixture. [mass of Ar = 1791.852 g, final P = 28.55 bar]
50. An unknown ga (X) at 2.0 atmosphere and Ar (40) at 1.0 atmosphere were injected simultaneously from the
two ends of a 1.0 metre long glass tube and the first collision between X and Ar occurred at a distance of 38
cm from Ar – end. Determine the molar mass of X assuming that gases were injected at same temperature an
through the pin-hole of identical geometry. [60 amu]
CHAPTER PRACTICE PROBLEMS
CHEMISTRY
FIITJEE
51. A 100 mL mixture containing 72% of CH4 by volume and the rest an unknown a gas ‘X’ was kept in a vessel.
Due to a very fine crack, the mixture effused out. 21 mL of the mixture was lost and the remaining mixture
contained 68.35% of methane by volume. Molecular mass of gas X is (all the measurements are made at
same temperature and pressure).
(A) 100
(B) 87.1
(C) 95.2
(D) none of these
Ans: [B]
52. Cl2O7 gas decomposes as:
Cl2O7 à Cl2 + O2
A partially decomposed gaseous mixture allowed to effuse through a pin – hole and the gas coming out
initially was analyzed. The mole fraction of the O2 was found to be 0.60, determine the degree of dissociation.
[0.2]
0
53. A mixture consisting of 80 mole per cent hydrogen and 20 mole per cent deuterium at 25 C and a total
2
pressure of 1 atm is permitted to effuse through a small orifice of area 0.20 mm . Calculate composition of the
initial gas that passes through.
[5.65 : 1]
54. The rate of diffusion of a sample of ozonised oxygen is 0.98 times more than that of pure oxygen. Find the
percentage (by volume of ozone in the ozonised sample.
[8.25%]
55. A vessel of volume 100 mL contains 10% of oxygen and 90% of an unknown gas. The gases diffuse in 86
seconds through a small hole of the vessel. If pure oxygen, under the same conditions, diffuse in 75 seconds,
find the molecular weight of the unknown gas.
[43.2]
Vapour Density
o
56. How many g of oxygen is contained in 10.5 L of oxygen measured over water a t 25 C and 740 torr?
o
Aqueous tension of water at 25 C is 24 torr
(A) 12.9 g
(B) 21.9 g
(C) 02.9 g
(D) 31.9 g
57. The total pressure of a sample of methane collected over water is 735 torr at 29 0C. The aqueous tension
at 290C is 30 torr. What is the pressure exerted by dry methane?
[0.12g; 0.64g]
Dalton’s Law
58. A mixture of hydrogen and oxygen at one bar pressure contains 20% by weight of hydrogen. Calculate partial
pressure of hydrogen.
0
59. 1 g of N2 and 1 g of O2 are put in a two-litre flask at 27 C. Calculate partial pressure of each gas, the total
pressure and the total pressure and the composition of the mixture in mole percentage.
[0.44 atm.; 0.80 atm.; 53.3%; 46.7%]
60. The mixture of gas at 760 torr contains 55.0% N2, 25.0% O2 and 20% CO2 by vol. What is partial pressure of
each gas in torr?
(A) 418 : 190 : 152 torr
(B) 190 : 418 : 152 torr
(C) 418 : 152 : 190 torr
(C) 152 : 418 : 190 torr
CHAPTER PRACTICE PROBLEMS
CHEMISTRY
FIITJEE
Eudiometry
61. 20 ml of CO was mixed with 50 mL of oxygen and the mixture was exploded on cooling, the resulting mixture
was shaken with KOH. Find the volume of the gas that is left.
(Ans : 40ml)
62. 10ml of a gaseous hydrocarbon was burnt completely in 80 mL of O2 at NTP. The remaining gas occupied 70
mL at NTP. This volume became 50 mL on treatment with KOH solution. What is the hydrocarbon?
(Ans : C2H4 )
63. 16mL of a hydrocarbon gas was exploded with excess of oxygen. On cooling, the volume of the resulting
gaseous mixture was reduced by 48 mL. when KOH was added, there was a further decrease of 48 mL in the
volume. Find the molecular formula of the compound.
(Ans : C3H6 )
64. 7.5 mL of a hydrocarbon gas was exploded with excess of oxygen. On cooling, it was found to have
undergone a contraction of 15 mL. If the vapour density of the hydrocarbon is 14, determine its molecular
formula. (C = 12, H = 1)
(Ans : C2H4 )
65. 50 mL of a mixture of CO and CH4 was exploded with 85 mL of O2 . The volume of CO2 produced was 50 mL
. calculate the percentage composition of the gaseous mixture if all volumes are measured under the same
conditions, and the given volume of O2 is just sufficient for the combustion of 50 mL of the mixture of CO and
CH4 .
(Ans : 20%)
66. 5 mL of a gas containing C and H was mixed with an excess of oxygen (30 mL) and the mixture exploded by
means of an electric spark. After the explosion the volume of the mixed gases remaining was 25 mL. On
adding a concentrated solution of KOH, the volume further diminished to 15 mL, the residual gas being pure
oxygen. All volumes have been reduced to NTP. Calculate the molecular formula of the hydrocarbon gas.
(Ans : C2H4 )
67. When a mixture consisting of 10 moles of SO2 and 15 moles of O2 was passed over a catalyst, 8 moles of
SO3 was formed. How many moles of SO2 and O2 did not enter into the reaction?
[Ans : SO2 : 2moles O2 : 11 moles]
68. 10 ml mixture of ethane and thane requires 7 ml of H2 for complete catalytic reduction. However, after
partial reduction, 33 ml of oxygen were required for complete oxidation of the same volume. The volume of H2
that was absorbed during partial reduction was
(A) 3 ml
(B) 4 ml
(C) 2 ml
(D) 3.5 ml
69. A gaseous hydrocarbon required two and half times of its volume of O2 for complete combustion and
produces double its volume of CO2. The molecular formula of the gas is
(A) CH4
(B) C2H6
(C) C2H2
(D) C2H4
70. A definite amount of a gaseous hydrocarbon having less than 5 carbon atoms was burned with sufficient
amount of O2. The volume of all reactants was 600ml, after the explosion the volume of the products was
found to be 700 ml under the similar conditions. The molecular formula of the compound is
(A) CH4
(B) C2H6
(C) C3H8
(D) C4H10
CHAPTER PRACTICE PROBLEMS
CHEMISTRY
FIITJEE
71. A mixture of CH4 and C2H2 occupies a certain volume at a total pressure of
70.5 mmHg. The sample is burnt, formed CO2 and H2O. The H2O is removed and the remaining CO2 is found
to have a pressure of 96.4 mmHg at the same volume and temperature as the original mixture. What
mole fraction of the gas was C2H2?
(A) .631
(B) 25.9
(C) 0.368
(D) 44.5
Ans: [C]
X gas
P
Compressibility
Factor (z)
72. The correct statement for the ‘X’ gas according to the given curve for X at
two different temperature is
(A) At point P, VReal < Videal, z > 1 and the assumption of kinetic
theory of gases (i.e. the volume of the gas molecules is negligible with
respect to volume of the gas) is valid.
(B) At point Q, VReal < Videal, z < 1 and the assumption of kinetic theory
of gases (i.e. the volume of the gas molecules is negligible with respect
to the volume of the gas) is valid.
(C) At point R, the temperature of gas X is lower than the temperature
at point Q.
(D) At point P, the repulsion between gas molecules is less than the
repulsion at point S.
•
•
S
R
X gas
1
•
•
Q
Pressure
73. The pressure of nitrogen gas and water vapours of 380 K are 0.7 atm and 0.3 atm in a 3L closed container. If
the whole gaseous mixture is transferred into 6l closed container then the total pressure of the gaseous
mixture under identical conditions is
(A) 2atm
(B) 0.5atm
(C) 0.65atm
(D) 1.7atm
74. Choose the correct statement for gas molecules.
(A) for an ideal gas compressibility factor is a function of pressure and temperature.
(B) for repulsive forces to operate z < 1.
(C) for attractive forces to operate z > 1
(D) for real gas compressibility factor depends on pressure and temperature.
75. For the real gases to obey vander Waal equation at critical pressure and temperature, the value of
compressibility factor should be
(A) 1
(B) 0.375
(C) greater than 1
(D) less than 1
76. Choose the correct statement.
(A) above critical temperature only gaseous state exists.
(B) for deviation from ideal behavior of gas only attractive force are responsible.
(C) only size factor decides the amount of deviation in a gas sample from ideal behaviour
(D) all statements are correct.
Y
X
Compressibility
Factor (z)
77. The correct statement for the ‘X’ & ‘Y’ gas according to the given curve at
the same temperature
(A) gas ‘Y’ is less polar than gas ‘X”
(B) gas ‘Y’ has lower critical temperature than gas ‘X’ if the gas
molecules have same size.
(C) gas ‘Y’ has higher Boyle’s temperature than ‘X’ if the gas
molecules have same size.
(D) all of these
1
Pressure
78. Which of the following statement is not true.
(A) the rate of diffusion of gas x (molecular wt. 16) at 4 atm pressure is equal to the rate of diffusion of gas y
(molecular wt. 25) at 5 atm pressure under identical conditions.
(B) the vrms decreases on decreasing the temperature.
(C) at Bolye’s temperature, for a real gas [PRe al ×VRe al ] = [Pideal ×Videal ]
(D) none of these
79. The r. m. s velocity of hydrogen is
then
7 times the r. m. s. velocity of nitrogen. If T is the temperature of the gas,
CHAPTER PRACTICE PROBLEMS
FIITJEE
(D) T(H2) =
(A) T(H2) = T(N2)
(B) T(H2) > T(N2)
CHEMISTRY
(C) T(H2) < T(N2)
7 T(N2)
80. If two gases A and B have freezing points -1700 C and – 1000 respectively. Select the correct statement from
the following
(A) compressibility factor of gas A is more than gas B
(B) Compressibility factor of gas A is less than gas B
(C) Both have same compressibility factor
(D) None of these
81. The values of Vander Waal’s constant (a) for gases O2, N2, NH3 and CH4 are 1.36 , 1.39, 4.17 and 2.253 L
atm mol
(A) O2
–2
2
respectively. The gas which can most easily be liquefied is
(B) N2
(C) NH3
(D) CH4
82. The empirical formula of an organic compound containing carbon and hydrogen is CH2. The mass of one litre
of this organic gas is exactly equal to that of one litre of N2. Therefore, the molecular formula of the organic
gas is
(A) C2H4
(B) C3H6
(C) C6H12
(D) C4H8
83. The vapour density of a gas is 11.2. The volume occupied by 11.2 g of the gas at S.T.P. will be
(A) 11.2 L
(B) 22.4 L
(C) 1 L
(D) 44.8 L
84. At what temperature, the rate of diffusion of N2 would be 1.625 times the rate of effusion of SO2 at 500C?
(A) 110 K
(B) 173 K
(C) 279 K
(D) none of these
85. 1 mol of a gaseous aliphatic compound CnH3nOm is completely burnt in an excess of oxygen. The
contraction in volume at room temperature is
1
3 ⎞
3
1 ⎞
1
3 ⎞
⎛
⎛
⎛
(A) ⎜ 1 + n − m ⎟
(B) ⎜ 1 + n − m ⎟
(C) ⎜ 1 − n − m ⎟
(D)
2
4 ⎠
4
4 ⎠
4 ⎠
⎝
⎝
⎝ 2
1 ⎞
⎛ 3
⎜ 1 − 4 n − 2 m ⎟
⎝
⎠
86. Which of the following gaseous mixture at room temperature does not follow Dalton’s law of partial pressure
(A) CO and CO2
(B) NO2 and O2
(C) SO2 and CO2
(D) HCl(g) and
NH3(g)
87. At STP, the order of mean square velocity of molecules of H2, N2, O2 and HBr is
(A) H2 > N2 > O2 > HBr
(B) HBr > O2 > N2 > H2
(C) HBr > H2 > O2 > N2
HBr
(D) N2 > O2 > H2 >
88. 50 ml of H2 diffuse out through a small hole of a vessel in 20 minutes. The time taken by 40 ml of oxygen to
diffuse out through same hole is
(A) 8 minutes
(B) 12 minutes
(C) 32 minutes
(D) 64 minutes
Paragraphs for Question
The real gases are those gases that shows the deviation from the ideal behaviour i.e., from ideal gas equation. To
determine the deviation from ideality we can define a term “Compressibility factor (Z)”. At high temperature and
low pressure the real gases have almost ideal behaviour
89. The value of Z which is not possible for a gas
(A) Z = 1
(B) Z > 1
(C) Z < 1
(D) Z = 0
90. Which of the following 1 mole of mixture will have the almost same value of compressibility factor (Z) as the
individual gas (1 mole) of mixture
(A) H2 and He
(B) NO2 and H2
(C) NH3 and H2
(D) C6H6 and H2
91. The value of Z for real gas is
(PV ) ideal
(PV ) ideal
(A)
(B)
RT
(PV )Re al
(C)
(PV )Re al
(PV ) ideal
(D) none of these
CHAPTER PRACTICE PROBLEMS
CHEMISTRY
FIITJEE
92. Match Column – I with Column – II (+8, +2, 0)
Column – II
(Variation in compressibility
Column – I (Conditions)
factor)
(A)
(B)
-2
(P+ aV )V = RT
At high temperature and low
pressure
(P)
Z >1
(Q)
Z<1
(C)
P(V – b) = RT
(R)
Z =1
(D)
At Boyle’s temperature
(S)
Z=0
[Ans: A – Q, B – R, C – P, Q – R]
93. Two gases A and B having densities 8 g/ml and 12 g/ml are mixed. The composition of ‘A’ and ‘B’
respectively in terms of percentage by volume is [density of mixture = 10.2 g/ml]
(A) 55, 45
(B) 45, 55
(C) 50, 50
(D) 60, 40
94. A sample of gaseous PCl5 at 5 atm and 100 K is heated to 400 K, where by pressure rises to 30 atm. If
volume of the container is kept constant, then degree of dissociation of PCl5 sample is
(A) 40 %
(B) 55 %
(C) 50 %
(D) 25 %
⎛
an 2 ⎞
95. In the vander Waal equation ⎜ P + 2 ⎟ (V − nb ) = nRT the term ‘P’ represents
V ⎠
⎝
(A) ideal pressure of real gas.
(B) actual pressure of real gas.
(C) molecular interaction.
(D) pressure correction term after taking size factor of gaseous molecules into account
96. The ratio of vander Waals constants a/b has the same dimension as that of
-1
-2
(A) energy mol
(B) energy × mole
(C) energy.mol
(D) energy
97. If Vrms (H2 at T1K ) is equal to Vrms (O2 at T2K ) then ratio T1 : T2 is
(A) 16
(B) 4
(C) 1/16
(D) 1/8
98. The density of O2 gas will be will be maximum at
(A) 1 atm, 300 K
(B) 2 atm, 100 K
50K
(C) 3 atm, 100 K
(D) 4 atm,
99. Under what condition of pressure and temperature, chlorine gas is expected to follow PV = nRT
(A) 20 atm, 100 K
(B) 25 atm, 200 K
(C) 0.5 atm, 800 K
(D) 20 atm,
500 K
100. For an ideal gas Ζ depends on which powers of pressure and temperature?
(A) 1, 0
(B) 2, 0
(C) 0, 0
(D) 1, 1
101. 2NH4NO3 → 2N2 (g ) + 4H2O (g ) + O2 (g ). After decomposition of NH 4 NO3 . The total pressure developed is
7 atm, mole fraction of N2 will be.
(A) 1/7
(B) 2/9
(C) 4/7
(D) 2/7
(A)
2RT
M
(B)
3RT
M
Fraction of
molecule
102. The molecular speed represented at point ‘P’ as shown in given curve can be calculated
using the formula.
P
Velocity
CHAPTER PRACTICE PROBLEMS
FIITJEE
(C)
CHEMISTRY
8RT
M
(D) any one of
these
SECTION – B (Multiple Choice Questions)
103. Which of the following represent best the behavior of an ideal gas?
(A)
(B)
(C)
(D) none of these
log P
log V
P
log V
log T
V
104. The incorrect statements given below is (are)
(A) compressibility factor for an ideal gas depends on pressure and temperature.
an 2
(B)
accounts for intermolecular force operating in ideal gas.
V2
⎛
an 2 ⎞
(C) ⎜ P + 2 ⎟ (V − nb ) = nRT is valid for real gases only.
V ⎠
⎝
(D) density of an ideal gas dosen’t depend on pressure and temperature.
105. Density of an ideal gas can be affected by
(A) pressure
(B) temperature
106.
(C)
(D) T 2 / 3
pressure
Choose the correct statement(s).
(A) at low pressure expression of Z involve ‘a’ not ‘b’.
(B) at high pressure expression of Z involve b not a
(C) at high temperature and low pressure expression of Z involves both a and b
(D) at high temperature and low pressure expression of Z involves neither a nor b
107. The average kinetic energy of 0.6 mole of an ideal gas is 1.496 KJ, the temperature of the gas is
(A) 200° C
(B) - 73° C
(C) 200 K
(D) – 73 K
COMPREHENSION
A mixture of Na2CO3 and NaHCO3 has a mass of 22 g. When this mixture is treated with HCl, 6 liters of triatomic,
linear and gaseous species is formed. If system is maintained at 25° C and at 0.947 atm pressure. Answer the
following questions using necessary concept. [ Also assume that no reactant is left in excess]
Read the above paragraph carefully and answer the questions given below it :
108. The moles of gaseous species formed is
(A) 0.232
(B) 0.0023
(C) 0.0096
109. Mole fractions of NaHCO3 and NaHCO3 are respectively
(A) 0.49, 0.51
(B) 0.51, 0.49
(C) 0.69, 0.31
(D) 2.77
(D) 0.31, 0.69
110. The percentage by mass of NaHCO3 is
(A) 55
111. Match the Column
(B) 35
(C) 45
(D) 22
CHAPTER PRACTICE PROBLEMS
FIITJEE
Column I
Column II
A.
Root mean square speed
P.
Proportional to
T
B.
Average speed
Q
Proportional to
1
M
C.
Most probable speed
R.
D.
Rate of diffusion
S.
E.
1
ρ( idea l gas )
CHEMISTRY
T.
3P
ρ
Possessed by most of molecules
2P
P
[ P = Pressure, ρ = Density, T = temperature, M = molecular mass]