NEET Chemistry Gaseous State MCQs Set E

Question. A cylinder of capacity 20 litres is filled with H₂ gas. The total average kinetic energy of translatory motion of its molecules is1.5x10⁵ J.The pressure of hydrogen in the cylinder is:
a. 2×10⁶ N /m²
b. 3×10⁶ N /m²
c. 4×10⁶ N /m²
d. 5×10⁶ N /m²
Answer : D

Question. A gas at a certain volume and temperature has pressure 75 cm. If the mass of the gas is doubled at the same volume and temperature, its new pressure is:
a. 37.5 cm
b. 75 cm
c. 150 cm
d. 300 cm
Answer : C

Question. If 20 cm³ gas at 1 atm. is expanded to 50 cm³ at constant T, then what is the final pressure:
a. 20 x 1/50
b. 50 x 1/20
c.  1 x 1/20 x 50
d. None of these
Answer : A

Question. 400 cm3 of oxygen a 27°C were cooled to –3°C without change in pressure. The contraction in volume will be:
a. 40 cm³
b. 30 cm³
c. 44.4 cm³
d. 360 cm³
Answer : A

Question. How many moles of He gas occupy 22.4 litres at 30°C and one atmospheric pressure?
a. 0.90
b. 1.11
c. 0.11
d. 1.0
Answer : A

Question. 16 g of oxygen and 3 g of hydrogen are mixed and kept at 760 mm pressure and 0°C. The total volume occupied by the mixture will be nearly:
a. 22.4 litres
b. 33.6 litres
c. 448 litres
d. 44800 ml
Answer : D

Question. At room temperature, the rms speed of the molecules of certain diatomic gas is found to be 1930 m/s. The gas is:
a. H₂
b. F₂
c. O₂
d. Cl₂
Answer : A

Question. Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will:
a. Increase
b. Decrease
c. Remain same
d. Decrease for some, while increase for others
Answer : C

Question. The speeds of 5 molecules of a gas (in arbitrary units) are as follows: 2, 3, 4, 5, 6. The root mean square speed for these molecules is:
a. 2.91
b. 3.52
c. 4.00
d. 4.24
Answer : D

Question. The molecules of a given mass of a gas have a rms velocity of 200m/sec at 27°C and 1.0 x 10⁵ N/m² pressure.
When the temperature is 127°C and pressure is 0.5 x 10⁵ N/m² , the rms velocity in m/sec will be:
a. 100√2/3
b. 100√2
c. 400/√3
d. None of these
Answer : C

Question. At which of the following temperature would the molecules of a gas have twice the average kinetic energy they have at 20°C?
a. 40°C
b. 80°C
c. 313°C
d. 586°C
Answer : C

Question. A vessel contains a mixture of one mole of oxygen and two moles of nitrogen at 300 K. The ratio of the average rotational kinetic energy per O₂ molecule to that per N₂ molecule is:
a. 1 : 1
b. 1 : 2
c. 2 : 1
d. Depends on the moments of inertia of the two molecules
Answer : A

Question. The average translational energy and the rms speed of molecules in a sample of oxygen gas at 300K are 6.12×10^–21J and 484m/s respectively. The corresponding values at 600K are nearly: (assuming ideal gas behaviour)
a. 12.45 x 10 ⁻²¹ J,968m/ s
b. 8.78 × 10 ⁻²¹ J,684m/ s
c. 6.21 x 10 ⁻²¹ J,968m/ s 
d. 12.42 x 10 ⁻²¹ J,684m/ s 
Answer : D

Question. The temperature at which RMS velocity of SO₂ molecules is half that of He molecules at 300K is:
a. 150 K
b. 600 K
c. 900 K
d. 1200 K
Answer : D

Question. The rms speed of 2 N molecules in a gas is u. If the temperature is doubled and the nitrogen molecules dissociate into nitrogen atoms, the rms speed becomes:
a. u / 2
b. 2u
c. 4u
d. 14u
Answer : B

Question. A gas at 27°C has a volume V and pressure P. On heating its pressure is doubled and volume becomes three times.
The resulting temperature of the gas will be:
a. 1800°C
b. 162°C
c. 1527°C
d. 600°C
Answer : C

Question. A flask is filled with 13 gm of an ideal gas at 27°C and its temperature is raised to 52°C. The mass of the gas that has to be released to maintain the temperature of the gas in the flask at 52°C and the pressure remaining the same is:
a. 2.5 g
b. 2.0 g
c. 1.5 g
d. 1.0 g
Answer : D

Question. If the value of molar gas constant is 8.3 J/mole-K, the n specific gas constant for hydrogen in J/mole-K will be:
a. 4.15
b. 8.3
c. 16.6
d. None of these
Answer : A

Question. At constant temperature on increasing the pressure of a gas by 5% will decrease its volume by:
a. 5%
b. 5.26%
c. 4.26%
d. 4.76%
Answer : D

Question. On 0°C pressure measured by barometer is 760 mm. What will be pressure on 100°C?
a. 760 mm
b. 730 mm
c. 780 mm
d. None of these
Answer : D

Question. A perfect gas at 27°C is heated at constant pressure to 327°C. If original volume of gas at 27°C is V then volume at 327°C is:
a. V
b. 3V
c. 2V
d. V/2
Answer : C

Question. A gas is filled in the cylinder shown in the figure. The two pistons are joined by a string. If the gas is heated, the pistons will:
a. Move towards left
b. Move towards right
c. Remain stationary
d. None of these
Answer : B

Question. The capacity of a vessel is 3 litres. It contains 6 gm oxygen, 8 gm nitrogen and 5 gm CO₂ mixture at 27°C. If R = 8.31 J/mole × kelvin, then the pressure in the vessel in N/m² will be: (approx.)
a. 5×10⁵
b. 5×10⁴
c. 10⁶
d. 10⁵
Answer : A

Question. A closed vessel contains 8g of oxygen and 7g of nitrogen. The total pressure is 10 atm at a given temperature. If now oxygen is absorbed by introducing a suitable absorbent the pressure of the remaining gas in atm will be:
a. 2 b. 10
c. 4 d. 5
Answer : D

Question. Temperature of an ideal gas is T K and average kinetic energy is E = 2.07 x 10^-23 T Joule/molecule. Number of molecules in 1 litre gas at S.T.P. will be:
a. 2.68×10²²
b. 2.68×10²⁵
c. 2.68×10²⁸
d. 1.68×10²²
Answer : A

Question. The average kinetic energy per molecule of helium gas at temperature T is E and the molar gas constant is R, then Avogadro’s number is:
a. RT/2E 
b. 3RT/E
c. E/2RT
d. 3RT/2E
Answer : D

Question. Under which of the following conditions is the law PV = RT obeyed most closely by a real gas?

a. High pressure and high temperature
b. Low pressure and low temperature
c. Low pressure and high temperature
d. High pressure and low temperature
Answer : C

Question. The equation of state of a gas is given by (P + aT²/V)V^c = (RT + b),where a, b, c and R are constants. The isotherms can be represented by P = AV^m − BVⁿ , where A and B depend only on temperature then?
a. m= −c and n = −1
b. m = c and n =1
c. m= −c and n =1
d. m = c and n = −1
Answer : A

Comprehension Based

Paragraph–I

Two gaseous molecules A and B are traveling towards each other. Let the mean free path of the molecule be σ and Z be the collision number with other molecules at pressure 1 atm.
Answer the following questions:

Question. The free path of a gas molecule is the distance:
a. Between the two opposite is the distance
b. That molecules travel in one second
c. Through which a molecule moves between two successive collisions
d. None of these
Answer : C

Question. If the mean free path is σ at 1 atm pressure, then its value at 5 atm pressure is:
a. 5σ
b. (2/5)σ
c. 5/σ
d. None
Answer : C

Question. If Z is the total number of collisions which a gas molecule registers with others per unit time under particular conditions, then the collision frequency of the gas containing N molecules per unit volume is:
a. Z/N
b. NZ
c. ZN
d. NZ/2
Answer : D

Question. If the collision frequency of a gas at 1 atm pressure is Z, then its collision frequency at 0.5 atm is:
a. 1.0 Z
b. 0.707 Z
c. 2 Z
d. 0.5 Z
Answer : B

Paragraph –II

The constant motion and high velocities of gas particles lead to some important practical consequences. One such consequence is that gases mix rapidly when they come in contact. Take the stopper off a bottle of perfume, for instance, and the odour will spread rapidly through the room as perfume molecules mix with the molecules in the air.
This mixing of different gases by random molecular motion and with frequent collision is called diffusion. A similar process in which gas molecules escape without collision through a tiny hole into a vacuum is called effusion. Both the processes follow Graham’s law which is mathematically put as r ∝ 1/ d. The average distance travelled by molecules between successive collisions is called mean free path.

Question. The stopcocks of the bulbs X (containing NH₃) and Y (containing HCl), both under identical conditions, are opened simultaneously. White fumes of NH₄Cl are formed at point B. If AB = 36.5cm, then BC is approximately:

a. 18.0 cm
b. 25.0 cm
c. 20.0 cm
d. 36.5 cm
Answer : B

Question. Select the incorrect statement (s).
a. The larger the size of the molecules, the smaller the mean free path
b. The greater the number of molecules per unit volume, smaller the mean free path
c. The larger the temperature, the larger the mean free path 
d. The larger the temperature, the smaller the mean free path
Answer : A

Question. X mL H₂ effuses through a hole in a container in 5 s. The time taken for the effusion of the same volume of the gas specified below under identical condition is:
a. 10 s : He
b. 20 s : O₂
c. 25 s : CO
d. 55 g : CO₂
Answer : B

Question. When CO₂ under high pressure is released from a fire extinguisher, particles of solid CO₂ are formed, despite the low sublimation temperature (–77ºC) at 1 atm because?
a. The gas does work pushing back the atmosphere using kinetic energy of molecules and thus lowering the temperature
b. The volume of the gas is decreased rapidly, hence, temperature is lowered
c. Both (a) and (b) are correct reasons
d. Neither (a) nor (b) is the correct reason
Answer : A

Question. Match the items of columns I and II:

a. A → 1; B → 2; C → 3; D → 4
b. A → 1; B → 3; C → 2; D → 4
c. A → 3; B → 2; C → 1; D → 4
d. A → 2; B → 1; C → 4; D → 3
Answer : B

Question. Match the items of columns I and II:

a. A→ 1; B→ 2; C→ 3; D → 4
b. A→ 2; B→ 3; C→ 4; D → 1
c. A→ 3; B→ 2; C→ 1; D → 4
d. A→ 2; B→ 1; C→ 4; D → 3
Answer : B

Comprehension Based

Paragraph –I

Mean free path of molecule is the average distance traveled by a molecule between two successive collisions and is given by λ = 1/√2πd² n where d is diameter of gas molecules, n number of molecules per unit volume.

Question. Which of the following statements is not correct for gas molecules?
a. Mean free path is inversely proportional to the square of diameter of gas molecules
b. Mean free path is inversely proportional to the molecular density of gas molecules
c. Mean free path is directly proportional to the pressure of gas
d. Mean free path is directly proportional to the temperature of gas
Answer : C

Question. The mean free path for air molecules at NTP is:
a. 1 Å
b. 10 Å
c. 100 Å
d. 1 mm
Answer : C

Question. Mean free path between molecules in a solid is of the order of:
a. 1 Å
b. 10 Å
c. 100 Å
d. 1 mm
Answer : A

Match the Column

Question. No gas perfect gas. Thus a real gas does not obey gas equation. It obeys van der Waal’s equation (P + a/V²) (V –b) = RT where a and b are constants. Behaviour of gas is assessed from the fact the under what conditions can it be liquefied. Gaseous state of matter is taken as gas if it cannot be liquefied by the application of pressure alone. For gas to behave as an ideal gas it has some variable  mentioned in column I. The values of these constant is mentioned in column II. Match the proper values of these constants for a gas.

a. A → 1; B → 2; C → 3
b. A → 3; B → 2; C → 1
c. A → 2; B → 1; C → 3
d. A → 1; B → 3; C → 2
Answer : D

Question. Degree of freedom of a molecule is the number of coordinates to be fixed to locate the position of a molecule. The degree of freedom helps us to know the energy possessed by a molecule in real gas at given absolute temperature because, according to law of ‘Equipartition of energy’. Energy is equally divided among all degrees of freedom. For different gas the mentioned in column I, the no. of degrees of freedom per molecule is:
      Column I                Column II
(A) Monoatomic gas     1. Always 3
(B) Diatomic gas           2. Always 5
(C) Poly atomic gas      3. 4
(D) Water                      4. 7
a. A → 1; B → 2; C → 3; D → 4
b. A → 4; B → 3; C → 2; D → 1
c. A → 3; B → 4; C → 1; D → 2
d. A → 2; B → 3; C → 4; D → 1
Answer : A

Integer

Question. Two identical cylinders contain helium at 3.5 atmosphere and argon at 2.5 atmosphere respectively. If both these gases are filled in one of the cylinder, what would be the pressure of the mixture?
Answer : 6

Question. From the relation PV = RT calculate the value of the constant R for one gram mole of an ideal gas.
Answer : 2

Question. A surface is hit elastically and normally by n balls per second, each of mass m moving with velocity u. If each ball is made to hit the same surface with velocity 2u, the force on the surface would become K times. What is the value of K?
Answer : 2

Question. The rms velocity of molecules of a gas at –73°C and 1 atmospheric pressure 100 m/s. The temp. Of the gas is increased to 527°C and pressure is doubled. The rms velocity becomes K times. What is the value of K?
Answer : 2

Question. Two gases A and B, having the same temp. T, same pressure P and same volume V are mixed. If mixture occupies a volume V and has temp. T, the pressure of the mixture will be x P, where x =?
Answer : 2

Question. Suppose ideal gas equation follows VP3 = constant. Initial temperature and volume of the gas are T and V respectively. If gas expand to 27V then its temperature will be come:
Answer : 9