Thermodynamics Questions and Answers

orrect 2 i ii correct 3 i iii correct The adiabatic bulk modulus of hydrogen gas y 1 4 at NTP is 1 1 x 105 N m 2 1 x 10 5 N m 4 1 4 x 105 N m 3 1 4 N m A given quantity of a gas is at pressure P and absolute temperature T The isothermal bulk modulus c 4 i correct

Section A Previous Year Questions AIP sip Two containers of equal volume contain the same gas at pressure p and p and absolute temperature T and T repectively On joining the vessels the gas reaches a common pressure p and common temperature T The ratio p T is equal to RPMT 2009 1 P Pisom P P T P T T T 2 bobaves as an ideal gas 3 P T P T T T 4 27 27 temperature and high pressure RPMT 2009

gas 1 In process AB work done by system is positive 2 In process AB heat is rejected out of the system 3 In process AB internal energy increases P B A T OR internal energy decreases and in process BC internal energy increases

P V and P V are initial and final pressures and volumes of a gas in a thermodynamic process respectively If PV constant then the amount of work done is Question Type Single Correct Type 1 minimum for n y 2 minimum for n 1 3 minimum for n 0 4 1 minimum for n x

In an isothermal reversible expansion if the volume of 96 gm of oxygen at 27 C is increased from 70 litres to 140 litres then the work done by the gas will be Question Type Single Correct Type 1 300 R log10 2 2 81 R loge 2 3 900 R log10 2 23 x 900 R log 2

April 2019 V The specific heats Cp and C of a gas of diatomic molecules A are given in units of J mol K by 29 and 22 respectively Another gas of diatomic molecules B has the corresponding values 30 and 21 If they are treated as ideal gases then a A has a vibrational mode but B has none b A has one vibrational mode and B has two c A is rigid but B has a vibrational mode d Both A and B have a vibrational mode each

1 kg of gaseous CO2 contained in a closed system undergoes a reversible process at constant pressure During this process 42 kJ internal energy is decreased Determine the work done during the process Take cp 840 J kg C and cv 600 J kg C

Two moles of an ideal gas undergoes the cyclic process abcda which is shown in the internal energy vs volume diagram The temperatures of the gas at b and d are 727 C and 327 C Calculate the net heat absorbed by the gas during the process a d V C 2V V

5 gm of ice at 0 C is mixed with 1gm 100 C The final temperature and composition of th mixture is 1 Water at 60 C 2 Water at 40 C 3 2gm water at 100 C and rest as steam 4 2gm water at 0 C and rest ice X

INEET 2013 26 A gas is taken through they cycle ABC A as shown What is the net work done by the gas 0 7 6 6x5 X10 X 4 3 2 2 1 0 a 2000 J p 105 Pa A 2 4 b 1000 J P T 6 B C 1x 0 8 c Zero 3 X 10 S S XI V 10 3 m Sylp d 20001

For froyoun 1 One mole of an ideal monatomic process described by the equation pV3 constant The heat capacity of the gas during this process is NEET 201 312 a R 5 b R 2 c 2R spes gas undergoes a al d R

Two distant stars X and Y are observed in the sky Star X emits blue light whereas Star Y emits red light Which of the following conclusions can you draw from the above observation ans Star X is brighter than Star Y Star X is younger than Star Y Star X is older than Star Y Star X is cooler that Star Y

1 30 k Assertion In adiabatic process change in internal energy is equal to work done on gas Reason In adiabatic process no heat exchange with surrounding 1 If both Assertion Reason are true the Reason is a correct explanation of the Assertion 2 If both Assertion and Reason are true but Reason is not a correct explanation of the Assertion 3 If Assertion is true but the Reason is false 4 If Assertion Reason both are false AIIMS 2018 If is given of the gas what is change in

4 If Assertion Reason both are false Two chambers containing m g and m g of a gas at pressure P and P respectively are put in communication with each other temperature remaining constant The common pressure reached will be AIIMS 2017 PP m m 1 P m P m 2 PP m P m P m m m P P P m Pm 4 m m P P m Pm constant pressure the fraction of the heat energy supplied which increases 3

An ideal gas is initially at temperature T and volume V Its volume is increased by AV due to an increase temperature AT pressure remaining constant The quantity 8 AV varies with temperature as VAT 1 T AT 2 THAT Tamn K T AT Temn k T AT

4 If Assertion Reason both are false A closed vessel explodes at 15 atm pressure If temperature of the vessel is 300 K at 10 atm pressure then find at w temperature will vessel explodes AIIMS 201 1 250 K 2 420 K 4 450 K 3 200 K

The temperature entropy diagram of a reversible engine cycle is given in the figure Its efficiency is AIEEE 2005 2T S 2S S 4 2 N

The volume V of a monoatomic gas varies with its temperature T as shown in the graph The ratio of work done by the gas to the heat absorbed by it when it undergoes a change from state A to state B is NEET 2018 410215 2 2 3 3 1 3 vd T 4 2 7 1 013 x 105 Nm2 requires 54 cal of heat energy to

1 C 3 C 5 2 C 4 C 6 3 C 3 C 2 Hydrogen gas is filled in a container of volume 20 litre Average translational kinetic energy of all its molecules is 1 5 x 105 J Pressure of hydrogen in cylinder is RPMT 2010 1 2 x 106 N m 2 3 x 106 N m 3 4 x 106 N m 4 5 x 106 N m 100gica at 0 C is put in water in bucket at 50 C On complete melting change in entropy will be Assuming no change IRPMT 20101

1 2 x 106 N m 2 3 x 10 N m 3 4 x 10 N m 4 5 x 100g ice at 0 C is put in water in bucket at 50 C On complete melting change in entropy will be Assuming no change in temperature of water RPMT 2010 1 4 5 cal K 2 4 5 cal K 3 5 4 cal K 4 5 4 cal K RPMT 2010 ninor of 44 8 litre volume monoatomic gas is filled up Heat required to raise temperature by 10 C will

Even Carnot engine cannot give 100 efficiency because we cannot 1 prevent radiation 2find ideal sources eliminate friction 3 reach absolute zero temperature od with 1 mole of a gas with y 5 3 then the 715

5 A diatomic gas initially at 18 C is compressed adiabatically to one eighth of its original volume The temperature after compression will be a 395 4 C c 18 C b 144 C d 887 4 C 1996

A certain quantity of O y 7 5 is compressed isothermally until its pressure is doubled P the gas is then allowed to expand adiabatically until its origional volume is restored then the final pressure P3 is term s of initial pressure P is 2 1 5 1 148 Question Type Single Correct Type 1 P 0 55 P 2 P3 0 76 P 3 P3 0 68 P 4 P 2 55 P

A refrigerator has to transfer an average of 268 Joule of heat per second from temperature 5 C t 35 C What is the average power consumed assuming ideal reversible cycle and no other losses Select one a 308 J S 1 b 288 J S c 309 J S 1 d 298 J S 1

A monoatomic gas undergoes a process given by 2dU 3dW 0 then the process is A isobaric B Adiabatic C polytropic processes with equation PV0 5 constant D polytropic processes with equation PV constant

In a constant volume gas thermometer the pressure of the working gas is measured by the difference in the levels of mercury in the two arms of a U tube connected to the gas at one end When the bulb is placed at the room temperature 27 0 C the mercury column in the arm open to atmosphere stands 5 00 cm above the level of mercury in the other arm When the bulb is placed in a hot liquid the difference of mercury levels becomes 45 0 cm Calculate the temperature of the liquid Atmospheric pressure 75 0 cm of mercury At constant volume po T P2 T2 P T 11 by attaching it P2 12 T 273 30 or T2 T 45 75 5 75 450 K 450 273

29 One mole of a gas isobarically heated by 40 K receives an amount of heat 1 162 kJ What is the ratio of specific heats of the gas a 1 7 b 1 4 c 1 3 d 1 5

Example 2 The figure shows a cross sectional view of a masonry dam whose length perpendicular to the diagram in 30 m The depth of water behind the dam is 10 m The masonry of which the dam is constructed has a density of 3000 kg m a Find the dimensions x and 2x if the weight of the dam is to be 10 times the horizontal force exerted on it by water Check the stability of the dam with respect to its overturning about the edge through point O b 10 m Water X dam 2x

35 A gaseous mixture consists of 16 g of helium and 16 g of oxygen The ratio mp a 1 62 of the mixture is Cv b 1 59 c 1 54 d 1 4

In a refrigerator the system extracts heat of 600 J from a cold reservoir and released 900 J of heat to hot reservoir The coefficient of performance of a refrigerator is given by NCERT Pg 314 1 2 3 6 2 3 4 9

30 The zeroth law of thermodynamics for three systems J K CET 2013 A B and C in contact demands that a A and B are in thermal equilibrium b B and Care in thermal equilibrium c A and Care in thermal equilibrium d A B and C are in thermal equilibrium

An ideal heat engine working between temperature T and T has efficiency n If both the temperature are raised by 50 K each then the new efficiency of heat engine will be Equal to n Less than n Greater than n Can t predict

If the energy input to a Carnot engine is thrice the work it performs then the fraction of energy rejected to the sink is opone 1850 30 Kerala CEE 2015 a 1 3 d 2 3 e 3 4 s with y 1 4 undergoes the adiabatic process of god by 0 5 b 1 4 c 2 5 mer

Hydrogen molecules mass m are in thermal equilibrium at a temperature T Assuming classical distribution of velocity the most probable speed at room temperature is a kgT m b 2k Tlm c 2k T m d m 2k T

will cool at same rate 2 A body cools down from 80 C to 60 C in 10 minutes when the temperature of surroundings is 30 C The temperature of the body after next 10 minutes will be 1 30 C 3 50 C 2 48 C 4 52 C

Objective Type Questions A uniform thermometre scale is at steady state with its 0 cm mark at 20 C and 100 cm mark at 100 C Temperature of the 60 cm mark is 2 68 C 4 58 C 1 48 C 3 52 C

Q28 If a cylinder containing a gas at high pressure explodes the gas undergoes A Reversible adiabatic change and fall of temperature B C D Reversible adiabatic change and rise of temperature Irreversible adiabatic change and fall of temperature Irreversible adiabatic change and

I PROBLEM SOLVING Solve the problems below using the step by step procedure that was previously taught in this module 4 points 7 10 Calculate the energy required to increase the temperature of 20g of water from 2000 to 100 OC Given Formula Solution Answer

The P V diagram 2 g of helium gas for a certain process A B is shown in the figure What is the heat given to the gas during the process A B P 2P Po A 0 C Vo 4P V B 5P V 6P V 2V V Correct Answer

3 A sample of 0 1 g of water at 100 C and normal pressure 1 013 x 105 Nm 2 requires 54 cal of heat energy to convert to steam at 100 C If the volume of the steam produced is 167 1 cc the change in internal energy of the sample is NEET 2018 1 104 3 J 3 84 5 J 2 208 7 J 4

6 Steam at 100 C is passed into 20 g of water at 10 C When water acquires a temperature of 80 C the mass of water present will be 008 1 Take specific heat of water 1 cal g C 1 and latent heat of steam 540 cal g AIPMT 2014 1 24 g 3 42 5 g and 2 31 5 g 0216 Yeunivers 4 22 5 g

In a container air is filled and maintained at temperature To Inner surface of walls of the container is maintained at temperature T At different values of temperatures T that are less than equal to and greater than To pressure exerted by the air on the container walls are P P2 and P3 respectively Which of the following statements is correct a P P P3 c P P P3 b P P P3 d P P P3 A piston can slide without friction inside a horizontal cylindrical vessel which contains an idool mot mi

between the pistons becomes 60 cm 16 Two rubber balloons filled with the same ideal gas when held at the bottom of a lake in thermal equilibrium with the surrounding water occupy equal volumes Rubber of the first balloon is a good conductor of heat while that of the second balloon is a good insulator of heat Both the balloons are set free simultaneously If temperature of water in the lake is uniform which balloon will occupy more volume when it comes near surface of the lake a The first balloon b The second balloon c Both the balloons will occupy equal volumes d Decision depends on the adiabatic exponent of the gas One mole of a mono atomin

X 3 Z y B A 25 A student in an experimental study of a process 1 2 3 on an ideal gas prepares two graphs to show relations between absolute temperature T pressure P and volume V Later he found that he has forgotten to specify a coordinate axis in each graph and marking states in the second graph Unspecified coordinates are shown by letters A and B and unspecified states by letters x y and z in the second graph Which of the following combinations best suits these graphs a A P B b A P B T x 1 y 2 z 3 T x 3 y 2 z 1 c A T B V x 3 y 2 z 1 d A T B T x 1 y 2 z 3 Questions 26 and 27 are based on the following physingl Two heat cond 1

5 ncrease An ideal gas changes in states from 1 to 2 through three different processes A B C as shown 10 A B C 4 25 A V Then work done during the processes are WA WB W Choose the correct option 1 W W W 3 W WC WB 2 WA WB W 4 WC WA WB A BCsfatda sa P A B 1 HW 1 W W W 3 W W W

In case of water from 0 C to 4 C i Volume decreases and density of water is maximum at 4 C ii AW will be negative since volume decreases iii Cp C V iv C C 1 i ii 3 iii iv 2 ii iii 4 i ii iv 17 18 ALLEN 0 C 4 C affery 1 4 C 1 iii C C iv C C 1 i ii 3 iii iv 2 ii iii 4 i ii iv

a given process on an ideal gas dW 0 24 dQ 0 then for the gas 1 Temp will decrease 2 Vol will increase 3 pressure will remain constant 4 Temp will increase a felu 1 2 34 3 fram 4

6 In T S diagram ratio of slope of an isobaric 6 curve and an isochoric curve is 1 Y 2 Y 3 y 4 Zero T S 1 Y 2 3 y

Consider four heat reservoirs A B C D An 7 engine working between A and C has an efficiency which is mean of efficiencies of same engine working between AB and AD Then absolute temperture of C will be A is source 1 Geometric mean of temperature of A D 2 Arithmetic mean of temperature of B D 3 Harmonic mean of temperature of A D 4 Sum of temperatures of A and D 1 2 BD 3 AD 4 AD A B C D C AND ADQUIER Gal Asia CRIER pat 34ff4

A block of ice at 0 C is slowly heated and converted into steam at 100 C Which of these curves represents the phenomenon quantitatively L Time 1 Time 2 Time Time 5 g ufafa faz al 1 L 319 4 3 244 2 ALLEN 100 C THE