Kinetic Theory of Gases PYQs Set 7 (PDF)

Set 7 of 8 · Questions 181-210 of 212

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Mere Teacher · Previous Year Questions NEET Physics · Kinetic Theory of Gases · Set 7 (Q181-210)
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181. $Following statements are given : (1) The average kinetic energy of a gas molecule decreases when the temperature is reduced. (2) The average kinetic energy of a gas molecule increases with increase in pressure at constant temperature. (3) The average kinetic energy of a gas molecule decreases with increases in volume. (4) Pressure of a gas increases with increase in temperature at constant pressure. (5) The volume of gas decreases with increase in temperature. Choose the correct answer from the options given below:$ (1) $(1) and (4) only$ (2) $(1), (2) and (4) only$ (3) $(2) and (4) only$ (4) $(1), (2) and (5) only$ 182. $The dimensions of Stefan's constant are$ (1) $M^{0} L^{1} T^{- 3} K^{- 4}$ (2) $M^{1} L^{1} T^{- 3} K^{- 3}$ (3) $M^{1} L^{2} T^{- 3} K^{- 4}$ (4) $M^{1} L^{0} T^{- 3} K^{- 4}$ 183. $At standard temperature and pressure the density of a gas is 1.3 kg/ m^{3} and the speed of the sound in gas is 330 m/sec. Then the degree of freedom of the gas will be$ (1) $3$ (2) $4$ (3) $5$ (4) $6$ 184. $The parameter that remains the same for molecules of all gases at a given temperature is :$ (1) $kinetic energy$ (2) $momentum$ (3) $mass$ (4) $speed$ 185. $The plot of isotherms will not be a straight line when a plot is drawn between :$ (1) $PV and V$ (2) $U and ρ (density)$ (3) $\frac{1}{P} vs \frac{1}{V}$ (4) $\frac{1}{U} and ρ$ 186. $According to kinetic theory of gases, which one of the following statements is wrong?$ (1) $All the molecules of a gas are identical.$ (2) $Collisions between the molecules of a gas and that of the molecules with the walls of the container are perfectly elastic.$ (3) $The molecules do not exert appreciable force on one another except during collision.$ (4) $The pressure exerted by a gas is due to the collision between the molecules of the gas.$ 187. $n mole of a perfect gas undergoes a cyclic process A B C A (see figure) consisting of the following processes - A \to B : Isothermal expansion at temperature T so that the volume is doubled from V_{1} to V_{2} = 2 V_{1} and pressure changes from P_{1} to P_{2} . B \to C : Isobaric compression at pressure P_{2} to initial volume V_{1} . C \to A : Isochoric change leading to change of pressure from P_{2} to P_{1} . Total work done in the complete cycle ABCA is -$ (1) $0$ (2) $nRT (ln 2 + \frac{1}{2})$ (3) $nRTIn 2$ (4) $nRT (ln 2 - \frac{1}{2})$ 188. $The plot that depicts the behavior of the mean free time T (time between two successive collisions) for the molecules of an ideal gas, as a function of temperature (T), qualitatively, is: (Graphs are schematic and not drawn to scale)$ (1) (2) (3) (4) 189. $10^{23} molecules of a gas, each having a mass of 3 \times 10^{- 27} kg strike per second per sq. cm of a rigid wall at an angle of 60^{\circ} with the normal and rebound with a velocity of 500 m / s . The pressure exerted by the gas molecules on the wall is (sin 30^{\circ} = cos 60^{\circ} = 0.5, cos 30^{\circ} = sin 60^{\circ} = 3 /2)$ (1) $500 N / m^{2}$ (2) $2000 N / m^{2}$ (3) $1500 N / m^{2}$ (4) $1000 N / m^{2}$ 190. $A cylindrical tube AB of length l, closed at both ends contains an ideal gas of 1 mol having molecular weight M . The tube is rotated in a horizontal plane with constant angular velocity ω about an axis perpendicular to AB and passing through the edge at end A, as shown in the figure. If P_{A} and P_{B} are the pressures at A and B respectively, then (Consider the temperature is same at all points in the tube)$ (1) $P_{B} = P_{A}$ (2) $P_{B} = P_{A} expMω2l2/3RT$ (3) $P_{B} = P_{A} expMω2l2/RT$ (4) $P_{B} = P_{A} expMω2l2/2RT$ 191. $Ratio of translational degrees of freedom to rotational degrees of freedom of a polyatomic linear gas molecule is$ (1) $1 : 1$ (2) $1 : 2$ (3) $2 : 3$ (4) $3 : 2$ 192. $A flask contains hydrogen and oxygen in the ratio of 2 : 1 by mass at temperature 27°C The ratio of average kinetic energy per molecule of hydrogen and oxygen respectively is :$ (1) $2 : 1$ (2) $1 : 1$ (3) $1:4$ (4) $4 : 1$ 193. $The correct relation between the degrees of freedom f and the ratio of specific heat γ is :$ (1) $f = \frac{2}{γ - 1}$ (2) $f = \frac{2}{γ + 1}$ (3) $f = \frac{γ + 1}{2}$ (4) $f = \frac{1}{γ + 1}$ 194. $By what percentage should the pressure of a given mass of a gas be increased so as to decrease its volume by 10% at a constant temperature?$ (1) $8.1%$ (2) $9.1%$ (3) $10.1%$ (4) $11.1%$ 195. $The number of vibrational degrees of freedom of a diatomic molecule is$ (1) $0$ (2) $1$ (3) $2$ (4) $3$ 196. $A flask contains argon and oxygen in the ratio of 3:2 in mass and the mixture is kept at 27°C. The ratio of their average kinetic energy per molecule respectively will be :$ (1) $3 : 2$ (2) $9 : 4$ (3) $2:3$ (4) $1 : 1$ 197. $The rms speeds of the molecules of Hydrogen, Oxygen and Carbondioxide at the same temperature are V_{H}, V_{O} and V_{C} respectively then :$ (1) $V_{H} > V_{O} > V_{C}$ (2) $V_{C} > V_{O} > V_{H}$ (3) $V_{H} = V_{O} > V_{C}$ (4) $V_{H} = V_{O} = V_{C}$ 198. $A gas has n degrees of freedom. The ratio of specific heat of gas at constant volume to the specific heat of gas at constant pressure will be :$ (1) $\frac{n}{n + 2}$ (2) $\frac{n + 2}{n}$ (3) $\frac{n}{2 n + 2}$ (4) $\frac{n}{n - 2}$ 199. $If one mole of an ideal gas at (P_{1}, V_{1}) is allowed to expand reversibly and isothermally (A to B) its pressure is reduced to one-half of the original pressure (see figure). This is followed by a constant volume cooling till its pressure is reduced to one-fourth of the initial value (B \to C) . Then it is restored to its initial state by a reversible adiabatic compression (C to). The net workdone by the gas is equal to :$ (1) $0$ (2) $- \frac{RT}{2 ( γ - 1 )}$ (3) $R T (ln 2 - \frac{1}{2 ( γ - 1 )})$ (4) $RTln 2$ 200. $At 300 K, the rms speed of oxygen molecules is \frac{α + 5}{α} times to that of its average speed in the gas. Then, the value of α will be (used π = \frac{22}{7})$ (1) $32$ (2) $28$ (3) $24$ (4) $27$ 201. $The internal energy (U) and the density (ρ) of an ideal gas follow the law Uρ = constant during a particular process. The same process will be correctly shown on a P-U diagram as -$ (1) (2) (3) (4) 202. $Two perfectly black spheres A and B having radii 8 cm and 2 cm are maintained at temperatures 127^{\circ} C and 527^{\circ} C respectively. The ratio of the energy radiated by A to that by B is$ (1) $1 : 2$ (2) $1 : 1$ (3) $2 : 1$ (4) $1 : 4$ 203. $For a gas having ' X' degrees of freedom, ' Y' is (γ =) ratio of specific heats (= \frac{C _{P}}{C _{V}})$ (1) $\frac{1 + X}{2}$ (2) $1 + \frac{X}{2}$ (3) $1 + \frac{2}{X}$ (4) $1 + \frac{1}{x}$ 204. $The pressure exerted by an ideal gas at a particular temperature is directly proportional to$ (1) $the mean speed of the gas molecules$ (2) $mean of the square of the speed of the gas molecules$ (3) $the square of the mean speed of the gas molecules$ (4) $the root mean square speed of the gas molecules.$ 205. $If R is universal gas constant, the amount of heat needed to raise the temperature of 2 moles of an ideal monoatomic gas from 273 K to 373 K when no work is done is -$ (1) $100 R$ (2) $150 R$ (3) $300 R$ (4) $500 R$ 206. $The root mean square speed of smoke particles of mass 5 x 1 0^{- 17} kg in their Brownian motion in air at NTP is approximately. [Given k = 1.38 x 1 0^{- 23} J K^{- 1}]$ (1) $60 mm s^{- 1}$ (2) $12 mm s^{- 1}$ (3) $15 mm s^{- 1}$ (4) $36 mm s^{- 1}$ 207. $Choose the correct P - V graph of ideal gas for given V - T graph.$ (1) (2) (3) (4) 208. $A partition divides a container having insulated walls into two compartments I and II. The same gas fills the two compartments (shown in figure). The ratio of the number of molecules in compartments I and II is-$ (1) $1 : 6$ (2) $6 : 1$ (3) $4 : 1$ (4) $1 : 4$ 209. $If the rms speed of oxygen molecules at 0^{0} C is 160m/s, find the rms speed of hydrogen molecules at 0^{0} C .$ (1) $640m/s$ (2) $40m/s$ (3) $80m/s$ (4) $332m/s$ 210. $What will be the effect on the root mean square velocity of oxygen molecules if the temperature is doubled and oxygen molecule dissociates into atomic oxygen?$ (1) $The velocity of atomic oxygen remains same$ (2) $The velocity of atomic oxygen doubles$ (3) $The velocity of atomic oxygen becomes half$ (4) $The velocity of atomic oxygen becomes four times$