NEET Chemistry Gaseous State MCQs Set A

Question. If the mean free path of atoms is doubled then the pressure of gas will become:
a. P/4
b. P/2
c. P/8
d. P
Answer : B

Question. Ratio of C_p and C_v of a gas 'X' is 1.4. The number of atoms of the gas 'X' present in 11.2 litres of it at N.T.P. is:
a. 6.02 ×10²³
b. 1.2 × 10²⁴
c. 3.01 × 10²³
d. 2.01 × 10²³
Answer : A

Question. At o 100 C and 1 atm, if the density of liquid water is 1.0 g cm³ and that of water vapour is 0.0006 g cm³, then the volume occupied by water molecules in 1 litre of steam at that temperature is:
a. 6 cm³
b. 60 cm³
c. 0.6 cm³
d. 0.06 cm³
Answer : C

Question. The density of a gas A n is three times that of a gas B. if the molecular mass of A is M, the molecular mass of B is:
a. 3 M
b. √3 M
c. M/3
d. M/√3
Answer : C

Question. The density of neon will be highest at:
a. S.T.P.
b. 0 ^oC,2atm
c. 273 ^oC,1atm
d. 273 ^oC,2atm
Answer : B

Question. What is the pressure of 2 mole of 3 NH at 27°C when its volume is 5 litre in vander Waal’s equation? (a = 4.17, b = 0.03711)
a. 10.33 atm
b. 9.33 atm
c. 9.74 atm
d. 9.2 atm
Answer : B

Question. For a gas the difference between the two specific heats is 4150 J/kg K. What is the specific heats at constant volume of gas if the ratio of specific heat is 1.4?
a. 8475 J/kg - K
b. 5186 J/kg - K
c. 1660 J/kg - K
d. 10375 J/kg - K
Answer : D

Question. The temperature of 5 mole of a gas which was held at constant volume was changed from 100^oC to 120^oC. The change in internal energy was found to be 80 J. The total heat capacity of the gas at constant volume will be equal to?
a. 8JK⁻¹
b. 0.8JK⁻¹
c. 4 JK⁻¹
d. 0.4 JK⁻¹
Answer : C

Question. The density of a polyatomic gas is standard conditions is 0.795 kgm^–3. The specific heat of the gas at constant volume is:
a. 930J-kg^–1 K⁻¹1
b. 1400J-kg^–1 K⁻¹
c. 1120J-kg^–1 K⁻¹
d. 925J-kg^–1 K⁻¹
Answer : B

Question. If two moles of diatomic gas and one mole of monoatomic gas are mixed with then the ratio of specific heats is:
a. 7/3
b. 5/4
c. 19/13
d. 15/19
Answer : C

Question. Two grams of hydrogen diffuse from a container in 10 minutes. How many grams of oxygen would diffuse through the same container in the same time under similar conditions?
a. 0.5 g
b. 4 g
c. 6 g
d. 8 g
Answer : A

Question. Volume of the gases produced at STP from 48.0g of carbon:
a. 179.2 L
b. 89.6 L
c. 44.8 L
d. 22.4 L
Answer : A

Question. Volume of 4.4 g of CO₂ at NTP is:
a. 22.4 L
b. 44.8 L
c. 2.24 L
d. 4.48 L
Answer : C

Question. The maximum number of molecules is present in:
a. 0.5 g of H₂ gas
b. 10 g of O₂ gas
c. 15 L of H₂ gas at STP
d. 5 L of N₂ gas at STP
Answer : C

Question. At 0°C and one atm pressure, a gas occupies 100 cc. If the pressure is increased to one and a half-time and temperature is increased by one-third of absolute temperature, then final volume of the gas will be:
a. 80 cc
b. 88.9 cc
c. 66.7 cc
d. 100 cc
Answer : B

Question. Equal amounts of two gases of molecular weight 4 and 40 are mixed. The pressure of the mixture is 1.1 atm. The partial pressure of the light gas in this mixture is:
a. 0.55 atm
b. 0.11 atm
c. 1 atm
d. 0.12 atm
Answer : C

Question. There are 6.02×10²² molecules each of N₂ ,O₂ and H₂ which are mixed together at 760 mm and 273 K. The mass of the mixture in grams is?
a. 6.2
b. 4.12
c. 3.09
d. 7
Answer : A

Question. At what pressure a quantity of gas will occupy a volume of 60 ml, if it occupies a volume of 100ml at a pressure of 720 mm? (while temperature is constant):
a. 700 mm
b. 800 mm
c. 100 mm
d. 1200 mm
Answer : D

Question. A 10g of a gas at atmospheric pressure is cooled from 273 ^oC to 0^oC keeping the volume constant, its pressure would become:
a. 1/2 atm
b. 1/273 atm
c. 2 atm
d. 273 atm
Answer : A

Question. Which one of the following indicates the value of the gas constant R ?
a. 1.987 cal K^–1 mol^–1
b. 8.3 cal K^–1 mol^–1
c. 0.0821 lit K^–1 mol^–1
d. 1.987 Joules K^–1 mol^–1
Answer : A

Question. Which of the following statements are correct?
a. An ideal gas can be liquefied at very low temperature and high pressure
b. At very high pressure, ‘b’ dominates over ‘a’ for a Van der Waal’s gas
c. For a real gas, there is no distinction between liquid and vapour state at critical condition
d. Easily liquefiable gases have higher Boyle’s temperature while the gases difficult to liquefy have lower Boyle’s temperature
Answer : BCD

Question. A open-ended mercury manometer is used to measure the pressure exerted by a trapped gas. Initially manometer shown's no difference in mercury level in both columns.
After sparing ‘A’ dissociates according to following reaction A(g) → B(g) + 3C(g)
If pressure of Gas ‘A’ decreases to 0.9 atm. Then (assume temperature to be constant and is 300 K)
a. Total pressure increased to 1.3 atm
b. Total pressure increased by 0.3 atm
c. Total pressure increased by 22.3 cm of Hg
d. Different in mercury level is 228 mm
Answer : ABD

Question. If gas expands at constant temperature:
a. The pressure decreases
b. K.E. of molecules remains the same
c. K.E. of molecules decreases
d. The number molecules of the gas increases
Answer : AB

Question. The kinetic energy of one mole of a gas is given by the two expressions K.E. =3PV/2 and K.E. = 3/2 RT
Hence, it can be said that:
a. K.E. ∝ P at constant temperature
b. K.E. ∝ P at constant pressure
c. K.E. is not directly proportional to volume at constant temperature
d. K.E. ∝ V at constant temperature
Answer : BC

Question. According to Van der Waal’s theory of non-ideal gases, which of the following prediction is/are correct?
a. H₂ and He are impossible to liquefy
b. For 3 NH , Z decreases more rapidly on increasing pressure than methane in lower pressure region
c. In the lower pressure region, Z decreases on increasing pressure; H₂ and He are exceptions to that
d. In the higher pressure region, Z increases with increasing pressure, H₂ and He are exceptions to that
Answer : ABC

Question. At what temperature the RMS velocity of oxygen molecules is equal to that of SO₂ at 300 K ?
(a) +123^ºC
(b) –123^ºC
(c) 27^ºC
(d) 600 K

Answer: B

Question. At very low pressure, the van der Waal’s equation for one mole is written as
(a) PV – pb = RT
(b) PV + a = RT
(c) PV = RT
(d) (P + a /V2)(V) = RT

Answer: D

Question. Values of van der Waal’s constant ‘a’ for three gases A, B and C are 5.6, 3.6 and 2.4 respectively.
The increasing order of their ease of liquefaction will be
(a) A, B, C
(b) C, B, A
(c) B, A, C
(d) B, C, A

Answer: B

Question. When 2 g of a gas A is introduced into an evacuated flask kept at 25ºC, the pressure is found to be one atmosphere. If 3 g of another gas B is then added to the same flask, the total pressure becomes 1.5 atmosphere. Asssuming ideal gas behaviour, calculate the ratio of molecular wt. MA: MB.
(a) 3 : 1
(b) 1 : 4
(c) 1 : 3
(d) None of these

Answer: A

Question. Equal time is taken by 100 ml hydrogen and 25 ml of a gas to diffuse through a porous partition. The mol wt. of the gas is
(a) 16
(b) 64
(c) 32
(d) None of these

Answer: C

Question. V ml of H₂ gas effuses through a hole in a container in 5 seconds. The time taken for the effusion of the same volume of the gas specified below under identical condition is
(a) 10 Seconds : He
(b) 20 Seconds : O₂
(c) 25 Seconds : CO
(d) 25 Seconds : CO₂

Answer: B

Question. A straight glass tube has two inlets X and Y at the two ends. The length of the tube is 200 cm. HCl gas through intel X and NH3 gas through inlet Y are allowed to enter the tube at the same time. White fumes first appear at a point P in side the tube. The distance of P from X is
(a) 81.12
(b) 0.8112
(c) 8.112
(d) None of these

Answer: A

Question. The temperature at which 5 moles of SO₂ will occupy a volume of 10 litres at a pressure of 15 atm.
using van der Waal’s constants a = 6.71 litre2 atm mole–1, b = 0.0564 litre mol–1
(a) 395.3 K
(b) 39.53 K
(c) 3953 K
(d) None of these

Answer: D

Question. A real gas approaches ideality at
(a) high temperature and high pressure
(b) high temperature and low pressure
(c) low temperature and low pressure
(d) low temperature and high pressure

Answer: B

Question. A container contains certain gas of mass m gm at a high pressure at P atm and temperature T k. A little amount of the gas was allowed to escape across a hole for sometime and then closed. Final temperature is 2/3 rd and final pressure is P/2 of the original. Then, calculate the ratio of the mass escaped and mass remained in the container?
(a) 2 : 1
(b) 1 : 4
(c) 4 : 1
(d) 10 : 1

Answer: B

Question. In a classroom there are 13 equidistant rows of benches and students are sitting on them. A class teacher releases laughing gas (N2O) from the front while a student releases tear gas (Molecular weight = 176) from the back of the classroom simultaneously then which row of students will laugh  and weep simultaneously?
(a) 4th
(b) 9th
(c) 6th
(d) 10th

Answer: B

Question. The ratio of velocities of diffusion of the gases A and B is 1 : 4. If the ratio of their masses is in the ratio of 2 : 3 (mixture) then ratio of their mole fraction is
(a) 10 : 1
(b) 1 : 10
(c) 24 : 1
(d) 1 : 24

Answer: D

Question. A hydrocarbon is composed of 85.7% carbon and 14.3% hydrogen by weight. It’s density is 2.28 gm lit–1 at 300 K and at 1 atm pressure. Then formula of the hydrocarbon is:
(a) C₂H₆
(b) C₃H₈
(c) C₄H₈
(d) C₄H₁₀

Answer: C

Question. A mixture of 0.5 mole CO and 0.5 mole CO₂ are contained in a container and allowed to effuse out across a pin hole into another vessel connected through a tube of negligible volume, which is vacant.
A total of “z” moles has effused in time “t” sec. If M1 and M₂ are the mean molar masses of gas mixture effused out and the gas mixture. Still remained in the first container then which one is correct?
(a) M₁z + M₂(1 – z) = 36
(b) M₁z + M₂(1 – 4z) = 10
(c) M2z + M₂(1 – z) = 36
(d) M₁z + M₂z = 2

Answer: A

Question. The composition of equilibrium mixture Cl₂ 2Cl which is attained at 1200°C is determined by measuring the rate of effusion through a pin-hole. It is observed that at 1.8 atm Hg, mixture effuses 1.16 time as that of Kr(Atomic weight = 84) effusing under the same condition. The % fraction of Cl₂ dissociated into Cl atoms is
(a) 1.37%
(b) 13.7%
(c) 20%
(d) 35.2%

Answer: B

Question. Which is true regarding kinetic theory of gases?
(a) The molecular volume is negligible in comparison to the total volume of the gas
(b) The force of attraction between the molecules of the gas is negligible
(c) The average kinetic energy of the gas molecules is directly proportional to the absolute temperature of the gas
(d) All of the above

Answer: D

Question. 20% N₂O₄ molecules are dissociated in a sample of gas at 27ºC and 760 torr. The density of equilibrium mixture is
(a) 3.116 gL^–1
(b) 10.9 gL^–1
(c) 1 gL^–1
(d) 0.5 gL^–1

Answer: A

Question. According to Maxwell-Boltzmann law of gases, the average translational energy (K.E.) is
(a) kT/2 per molecule
(b) kT per molecule
(c) RT per molecule
(d) 3/2 kT per molecule

Answer: D

Question. 1 mole N₂, 3 mole H₂ are mixed in 8.21 litres container at 300 K to form NH₃. If equilibrium average molecular mass was found to be 34/3 gm their total pressure of mixture (equilibrium) is
(a) 8 atm
(b) 4 atm
(c) 6 atm
(d) 9 atm

Answer: A

Question. At room temperature ammonia gas at 1 atm pressure and hydrogen chloride at p atmospheric pressure are allowed to diffuse through identical pin holes from opposite ends of a glass tube of 1 metre length and of uniform cross-section. Ammonium chloride is first formed at a distance of 60 cm from the end through which HCl gas is sent in. What is the value of p?
(a) 2.198 atm
(b) 21.9 atm
(c) 5.63 atm
(d) 1 atm

Answer: A