Thermodynamics PYQs Set 5 (PDF)

Set 5 of 16 · Questions 121-150 of 459

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Mere Teacher · Previous Year Questions NEET Physics · Thermodynamics · Set 5 (Q121-150)
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121. $7 mole of certain monoatomic ideal gas undergoes a temperature increase of 40K at constant pressure. The increase in the internal energy of the gas in this process is (Given R = 8.3 J K^{- 1} m o l^{- 1})$ (1) $5810 J$ (2) $3486J$ (3) $11620J$ (4) $6972J$ 122. $In an adiabatic change, the pressure and temperature of a monatomic gas are related as P \propto T^{c}, where C equals$ (1) $\frac{3}{5}$ (2) $\frac{5}{3}$ (3) $\frac{2}{5}$ (4) $\frac{5}{2} .$ 123. $The moment of inertia I of uniform rod about a perpendicular bisector increases to I + Δ I, if the temperature is increased slightly by Δ T . If the coefficient of linear expansion is α, then \frac{Δ I}{I} is (Assume (\frac{Δ T}{T} ≪ 1)$ (1) $α Δ T$ (2) $2 α Δ T$ (3) $3 α Δ T$ (4) $4 α Δ T$ 124. $A source supplies heat to a system at the rate of 1000 W. If the system performs work at a rate of 200 W. The rate at which internal energy of the system increases is$ (1) $600W$ (2) $800 W$ (3) $500 W$ (4) $1200 W$ 125. $A Carnot engine operating between two reservoirs has efficiency \frac{1}{3} . When the temperature of cold reservoir raised by x, its efficiency decreases to \frac{1}{6} . The value of x, if the temperature of hot reservoir is 99° C, will be:$ (1) $16.5 K$ (2) $33 K$ (3) $66 K$ (4) $62 K$ 126. $A gas does 4.5 J of external work during adiabatic expansion. If its temperature falls by 2 K, then its internal energy will be$ (1) $increased by 4.5 J$ (2) $decreased by 4.5 J$ (3) $decreased by 2.25 J$ (4) $increased by 9.0 J$ 127. $When a monatomic gas expands at constant pressure, the percentages of heat supplied that is used to do external work and to increase its internal energy are respectively$ (1) $40,60$ (2) $25,75$ (3) $60,40$ (4) $75,25$ 128. $A reversible engine converts one-sixth of the heat input into work. When the temperature of the sink is reduced by 62ºC, the efficiency of the engine is doubled. The temperatures of the source and sink are-$ (1) $8 0^{0} C, 3 7^{0} C$ (2) $9 5^{0} C, 2 8^{0} C$ (3) $9 0^{0} C, 3 7^{0} C$ (4) $9 9^{0} C, 3 7^{0} C$ 129. $The conclusion of second law of thermodynamics is that$ (1) $No heat engine can have efficiency η equal to zero.$ (2) $No heat engine can have efficiency η equal to one.$ (3) $No heat engine can have efficiency η greater than one.$ (4) $No heat engine can have efficiency η less than one.$ 130. $An ideal gas at temperature T, pressure p occupies a volume V . If its temperature is halved and pressure doubled, what is its new volume?$ (1) $\frac{V}{4}$ (2) $\frac{V}{2}$ (3) $V$ (4) $2 V$ 131. $An ideal gas heat engine operates in a Carnot cycle between 22 7^{o} C and 12 7^{o} C . It absorbs 6 kcal at the higher temperature. The amount of heat (in kcal) converted into work is equal to$ (1) $4.8$ (2) $3.5$ (3) $1.6$ (4) $1.2$ 132. $One mole of an ideal diatomic gas expands from volume V to 2 V isothermally at a temperature 27^{\circ} C and does W joule of work. If the gas undergoes same magnitude of expansion adiabatically from 27^{\circ} C doing the same amount of work W, then its final temperature will be (close to)____^{\circ} C . (log_{e} 2 = 0.693)$ (1) $-30$ (2) $-189$ (3) $-117$ (4) $-56$ 133. $110joule of heat is added to a gaseous system whose internal energy is 40 J, then the amount of external work done is$ (1) $150 J$ (2) $70 J$ (3) $110 J$ (4) $40 J$ 134. $In which of the following processes, heat is neither absorbed nor released by a system? [NEET 2019]$ (1) $Adiabatic$ (2) $Isobaric$ (3) $Isochoric$ (4) $Isothermal$ 135. $Match the Cp/Cv ratio for ideal gase s with different type of molecules Molecule Type Cp/Cv (A) Monatomic (I) 7/5 (B) Diatomic rigid molecules (II) 9/7 (C) Diatomic non-rigid molecules (III) 4/3 (D) Triatomic rigid molecules (IV) 5/3$ (1) $(A) - (II), (B) - (III), (C) - (I), (D) - (IV)$ (2) $(A)-(IV),(B)-(II),(C)-(I),(D)-(III)$ (3) $(A) - (IV), (B) - (I), (C) - (II), (D) - (III)$ (4) $(A) - (III), (B) - (IV), (C) - (II), (D) - (I)$ 136. $The temperature of the earth without greenhouse effect will be$ (1) $0^{\circ} C$ (2) $- 18^{\circ} C$ (3) $- 10^{\circ} C$ (4) $- 24^{\circ} C$ 137. $An electric fan is switched on in a closed room. The air in the room is$ (1) $cooled$ (2) $heated$ (3) $maintains its temperature$ (4) $heated or cooled depending on the atmospheric pressure$ 138. $1.00 kg of liquid water at 100^{\circ} C undergoes a phase change into steam at 100^{\circ} C at 1.0 atm (take it to be 1.00 \times 10^{5} Pa). The initial volume of the liquid water was 1.00 \times 10^{- 3} m^{3} which is changed to 2.001 m^{3} of steam. Findthe change in the internal energy of the system. [Use heat of vaporization = 2000 kJ / kg]$ (1) $1800 kJ$ (2) $200 kJ$ (3) $2000 kJ$ (4) $180 kJ$ 139. $A piece of metal has a weight of 49 gm in air and 39 gm in a liquid of density 1.2 \times 10^{3} kg / m^{3} kept at 32^{\circ} C . When the temperature of the liquid is raised to 45^{\circ} C the metal piece has a weight of 40 gm . If the density of the liquid at 42^{\circ} C is 1.0 \times 10^{3} kg / m^{3}, then the coefficient of linear expansion of the metal is$ (1) $83\times 1 0^{- 3} /°C$ (2) $113\times 1 0^{- 3} /°C$ (3) $13\times 1 0^{- 4} /°C$ (4) $43\times 1 0^{- 3} /°C$ 140. $The molar specific heat at constant pressure of an ideal gas is (7/2) R . The ratio of specific heat at constant pressure to that at constant volume is$ (1) $9/7$ (2) $7/5$ (3) $8/7$ (4) $5/7.$ 141. $In a heat engine, the temperature of the source of sink are 500 K and 375 K. If the engine consumes 25 \times 1 0^{5} J per cycle, the work done per cycle is$ (1) $6.25 \times 1 0^{5} J$ (2) $3 \times 1 0^{5} J$ (3) $2.19 \times 1 0^{5} J$ (4) $4 \times 1 0^{4} J$ 142. $A sample of O . 1 g ofwater at 10 0^{o} C and normal pressure (1.013 \times 1 0^{5} N m^{- 2}) requires 54 cal of heat energy to convert to steam at 10 0^{o} C . Ifthe volume ofthe steam produced is 167.1 cc, the change in internal energy of the sample, is$ (1) $104.3 J$ (2) $208.7 J$ (3) $42.2 J$ (4) $84.5 J$ 143. $A monatomic gas at a pressure P, having a volume V expands isothermally to a volume 2 V and then adiabatically to a volume 16 V . The final pressure of the gas is (Take γ = 5/3)$ (1) $64 P$ (2) $32 P$ (3) $P/64$ (4) $16 P$ 144. $A mass of diatomic gas (γ = 1.4) at a pressure of 2 atmospheres is compressed adiabatically so that its temperature rises from 2 7^{o} C to 92 7^{o} C . The pressure ofthe gas in the final state is$ (1) $8 atm$ (2) $28 atm$ (3) $68.7 atm$ (4) $256 atm$ 145. $A Carnot engine (E) is working between two temperatures 473 K and 273 K. In a new system two engines-engine E_{1} works between 473 K to 373 K and engine E2 works between 373 K to 273 K. If η_{12}, η_{1} and η_{2} are the efficiencies of the engines E, E_{1} and E2, respectively, then$ (1) $η_{12} = η_{1} η_{2}$ (2) $η_{12} \geq η_{1} + η_{2}$ (3) $η_{12} = η_{1} + η_{2}$ (4) $η_{12} < η_{1} + η_{2}$ 146. $5 kg of water at 20^{\circ} C is added to 10 kg of water at 60^{\circ} C . Neglecting heat capacity of vessel and other losses, then resultant temperature will be nearly$ (1) $35^{\circ} C$ (2) $40^{\circ} C$ (3) $47^{\circ} C$ (4) $28^{\circ} C$ 147. $A hole of diameter 5 cm is drilled in a metal sheet at 30^{\circ} C . The linear expansion of metal is 2 \times 10^{- 5} K^{- 1} . The diameter of the hole when the temperature is raised to 230^{\circ} C, is equal to$ (1) $5.01 cm$ (2) $5.02 cm$ (3) $5.03 cm$ (4) $5.04 cm$ 148. $A Carnot engine takes heat from a reservoir at 627^{\circ} C and rejects heat to a sink at 27^{\circ} C . Its efficiency will be$ (1) $3/5$ (2) $1/3$ (3) $2/3$ (4) $200/209$ 149. $The work of 146 kJ is performed in order to compress one kilo mole of a gas adiabatically and in this process the temperature of the gas increases by 7 ℃ . The gas is (R = 8.3 J m o l^{- 1} K^{- 1})$ (1) $diatomic$ (2) $triatomic$ (3) $mixture of monoatomic and diatomic$ (4) $monoatomic$ 150. $A work of 166.28 J is done to adiabatically compress one mole of a gas. If the increase in the temperature of the gas is 8^{\circ} C, the gas is (R = 8.314 J mol^{- 1} K^{- 1}))$ (1) $monatomic$ (2) $diatomic$ (3) $polyatomic$ (4) $mixture of diatomic and polyatomic$