Thermodynamics Questions and Answers

1 The pressure 1x 10 Nm2 of the air filled in a vessel is decreased adiabatically so much as to increase its volume three times The air pressure is y for air 14 log10 3 0 4771 log10 2 148 0 33206 a 2 14 x 104 Nm b 2 19 105 Nm 2 c 1 14 x 105 Nm d 3 14 104 Nm 2

3 One mole of an ideal monoatomic gas at temperature To 0 P V expands slowly according to the law constant If the final temperature is 27 heat supplied to the gas is a 2RT b RTO c 3 RTO 2 d 1 RTO 2

A ideal gas whose adiabatic exponent equals y is expanded so that the amount of heat transferred to the gas is equal to twice of decrease of its internal energy The equation of the Y 1 process is TV K constant where T and V are absolute temperature and volume respectively Then find the value of K

5 4 0 g of a gas occupies 22 4 litres at NTP The specific heat capacity of the gas at constant volume is 5 0 JK mol If the speed of sound in this gas at NTP is 952 ms then the heat capacity at constant pressure is Take gas constant R 8 3 JK mol 1 8 5 JK mol 2 8 0 JK mol 21 75 1 1 mot1 4 70 JK mol

1 N moles of a monoatomic gas is carried round the reversible rectangular cycle ABCDA as shown in the diagram The temperature at A is To The thermodynamic efficiency of the cycle is 2P P a 15 c 20 B A To Vo V D 2 b 50 d 25

the centre of earth is at a distance of 1 5 x 1011 m from the centre of sun the intensity of solar radiation reaching at the earth s surface is 1 26 kW m2 There is a spherical cloud of cosmic dust containing iron particles The melting point for iron particles in the cloud is 2000 K Find the distance of iron particles from the centre of sun at which the iron particle starts melting Assume sun and cloud as a black body o 5 6 x 10 8 W m K4 A 2 81 x 106 m C 2 81 x 10 m A circuit B 2 81 x 10 m D 1 40 x 10 10 m

40 T V curve of cyclic process is shown below number of moles of the gas are n Find the total work done during the cycle 1 MRT In 2 270 To A 2V Vo 2 nRT In 2 nRT In 2 3 4 2nRT In 2 2 hemin of 2 Kg h when the external temperature is 20 C Find the minimum which just prevents the ice from melting Latent

A gas has molar heat capacity C 4 5 R in the process PT constant The number of degrees of freedom of molecules in the gas is 3 6 I 3 4 5

38 An ideal gas expands according to the law p2V constant The internal energy of the gas 1 Increases continuously 2 Decreases continuously 3 Remain constant 1 Eirot in k p Sav QP V W P

The y air the temperature at 15 C If Test Series fo increases to 35 C the approximate percentage increase in pressure is ignore to expansion of tyre a 7 b 9 c 11 d 13

roblem 420 A resistor of resistance r 500 2 connected to an external battery is placed nder fitted with a frictionless piston of mass m 10 kg area of cross section 103 m and containing 2 es of an ideal monoatomic gas A current i 0 3 A flows through the U tance a If cylinder is thermally insulated at what speed u must the piston be moved upward in order that the temperature of the gas remains constant If the piston is fixed and cylinder is insulated find the rise in temperature of the gas after 30 second Take g 10 m s R 8 31 J mol K and atmospheric pressure Po 105 N m

D 21 J of heat energy is supplied to a diatomic ideal gas at constant pressure then change in internal energy of the gas is 1 10 J 3 15 J 2 12 J 4 18 J

The W O of a Carnot engine is 1 6 now the temperature of sink is reduced by 62 C then this ratio becomes twice therefore the initial temperature of the sink and source are respectively a 33 C 67 C c 67 C 33 C b 37 C 99 C d 97 K 37 K 2000

A mass of diatomic gas y 1 4 at a pressure of 2 atmospheres is compressed adiabatically so that its temperature rises from 27 C to 927 C The pressure of the gas in the final state is a 8 atm c 68 7 atm b 28 atm d 256 atm

done by the gas heat absorbed by the gas A cylindrical tube of uniform cross sectional area A is fitted with two air tight frictionless pistons The pistons are connected to each other by a metallic wire Initially the pressure of the gas is P and temperature is Tor Catmospheric pressure is also P Now the temperature of the gas is increased to 27 the tension in the wire will be A 2PA B PA wire PA 2 C D 4P A

7R Three moles of an ideal gas Cp at pressure P and temperature T is isothermally expand 2 to twice its initial volume V It is then compressed at constant pressure to its original volum Finally the gas is compressed at constant volume to its original pressure P a Sketch P V and P T diagrams b Calculate the net work done by the gas and heat transferred to the gas during the complete cycl

Two identical bodies are made of a material for which the heat capacity increases with temperature One of these is at 100 C while the other one is at 0 C If the two bodies are brought into contact then assuming no heat loss the final common temperature is NEET Phase 2 2016 1 50 C 2 More than 50 C 3 Less than 50 C but greater than 0 C 4 0 C

D It introduced the concept of the entropy The temperature entropy diagram of a reversible engine cycle is given in thefigure Its efficiency is A 1 2 C 1 3 B 1 4 D 2 3 in P 2To To So

If an ideal gas changes from state 1 to state 2 as shown in figure then the work done by the gas in the process will be BHU Screening 2012 a positive c zero P b negative d infinite A4 B C

BOX 5 A vessel of volume 8 3 x 10 m contains an ideal gas at temperature 27 C and pressure 200 kPa The gas is allowed to leak till the pressure falls to 100 kPa and temperature increases to 327 C What is the amoun of gas in moles will be leaked out

33 A diatomic gas undergoes a process represented by PV1 3 constant Choose the incorrect statement 1 The gas expands by absorbing heat from the surroundings TV0 3 2 The gas cools down during expansion TV 3 The work done by surroundings during expansion of the gas is negative 4 None of thoon

If for hydrogen Cp Cy m and for the nitrogen Cp Cv n where Cp and C refer to specific heat per unit mass at constant pressure and specific heat per unit mass at constant volume respectively The relation between m and n is A m 14n Correct Answer n 7n m 9n

An ideal monatomic gas is allowed to expa adiabatically so that its pressure and temperature are related as P CT then x is equal to C is a constant O 1 2 3 3 2 5 3 2 5 2

During isobaric process the thermal coefficient of volume expansion of an ideal gas at temperature T in K is 1 Zero 3 2T 2 2 T 1 4 Infinite

1 m c and n 1 An ideal gas expands in such a way that PV constant throughout the process 1 The graph of the process of T V diagram is a parabola 2 The graph of the process of T V diagram is a straight line Such an expansion is possible only with heating Such an expansion is possible only with 26

One mole of a monatomic ideal gas is taken along two cyclic processes E F G E and E FH E as shown in the PV diagram The processes invoked are purely isochoric isobaric Match the paths in List I with the magnitudes of the work done in List and select the correct answer using the codes given below the lists Q G H R F H S F G Codes P Q 3 1 2 36 P Ve 3 24 Po Vo 4 31 P Vo 160 P V In2 R 2 S 2

7 600 J of heat is added to a monatomic gas in a process in which the gas performs a work of 150 J The molar heat capacity for the process is A 3 R C 2 R B 4 R D 6 R

1 8 J K 3 4 0 J K 2 0 8 J K 4 0 4 J K 234 Monoatomic diatomic and triatomic gases whose initial volume and pressure are same are compressed till their volume become half the initial volume 1 If the compression is adiabatic then monoatomic gas will have maximum final pressure 2 If the compression is adiabatic then triatomic gas will have maximum final pressure 3 If the compression is adiabatic then their final pressure will be same 4 If the compression is isothermal then their final pressure will be different

One mole of ideal monoatomic gas is taken along a cyclic process as shown in the figure Process 1 2 shown is 1 4th part of a circle as shown by dotted line process 2 3 is isochoric while 3 1 is isobaric If efficiency of the cycle is n where n is an integer Find n 2P 0 P 0 2 3

One mole of oxygen of volume 1 litre at 4 atm pressure to attain 1 atm pressure by result of isothermal expansion Find work done by the gas 1 155 J 2 206 J wol 4 562 J 3 355 J

A scientist claims to have developed a heat engine working between 27 C and 727 C with efficiency x Which of the following values of x will make his claim right 1 60 2 75

154 A gas contained in a box of 0 1 m at atmospheric pressure is connected to another vessel of 0 09 m Consequent change in pressure is X mm of Hg Then X in metre is 1 0 4 2 0 5 3 0 36 4 0 3 85

A box of negligible mass containing one mole of an ideal monoatomic gas of molar mass M moves with constant speed V on a smooth horizontal surface If the box suddenly stops then change in the temperature of the gas will be R molar gas constant 1 3 MV 5R MV 2R 2 4 MV 3R MV R

cycle a b c d has the V T diagram shown below Process d a and b c are adiabatic V 1 3 2 The corresponding P V diagram for the process is all figures are schematic and not drawn to scale PA a b d 18 14 PA d C a b PA PA a d C d a C V V b C b C T

Two chambers with volumes V1 and V2 contain N and N2 molecules of a gas at the same temperature but at pressure P and P2 respectively Calculate the pressure of the mixture when the two chambers are put in communication P P x N N X N N PP N N PP N P N P 2 4 N N P P N P N P N N PP N P N P

Nitrogen gas is filled in an insulated container If a fraction of moles dissociates without exchange of any energy then the fractional change in its temperature is 1 3 5 3 2 BN 2 2257 4 a 3 5a 2 3 given h

05 The specific heat of an ideal gas depends on temperature is 1 2 T 3 T 4 Does not depends on temperature

5 Article Which of these scientists created laws to describe the relationship between temperature and volume 1 Point Gay Lussac Boyle O Avogadro

Section A 1 An ideal diatomic gas undergoes the cycle ABCA shown at right but not to scale AB is isobaric BC is adiabatic CA is isothermal TA is 500 K a Find n TB Tc Pc and Vc b Find Ws Q and AEth during A B in J c Find Ws Q A and AEth during B C in J 3 00 P atm B 0 500 1 000 V L d Find Ws Q and AEth during C A in J f Find QH Qc and Wcycle done by the cycle g Find the efficiency of the cycle and the max possible efficiency of a cycle operating at these temperatures h What would be the coefficient of performan whore this cycle is reversed

Three beakers containing the same volume of water at three different temperatures are placed in a room with air at 25 C 0 C 10 C Which of the following will be the most likely result 25 C 90 C O the beaker at 0 C will increase to 90 C O the temperature inside all three beakers and the air will eventually be the same O the surrounding room temperature will eventually be 100 C the amount of total energy in the water molecules for all three beakers will increase

11 How much energy does it take to raise the temperature 50 0 g of ethyl alcohol by 5 00 C 1 Point 250 J 0 25 J O 615 J O 6150 J

21 How much total heat is required to transform 1 65 liters of liquid water that is initially at 25 0 C entirely into H O vapor at 100 C Convert your final answer to megajoules MJ Laulima contains a unique randomized value for the volume of water Assume rapid heat transfer within the system and that the system is fully insulated from its surroundings Physical values for H O although you may not need to use all of them Cliquid water 4186 J kg K Lf 334 000 J kg Ly 2 256 000 J kg

The gas in a cylinder expands and forces a piston outward During this process the gas has a constant pressure of 3 15x105 Pa The volume in the cylinder changes from 9 60x10 4 to 1 00x10 3 m3 The work done on the gas is 12 6J 303J 315 J O 12 6J

In this diagram of a cyclic process the three legs of the cycle can be classified as in no particular order P T1 T2 T1 isothermal adiabatic isobaric Oisochoric isobaric isothermal O isobaric isochoric isovolumetric isochoric isobaric isentropic none of the above

Can we transfer 5 kWh of heat to an electric resistance wire and produce 6 kWh of electricity Yes or No Yes No

A mass of 2 5 kg of saturated water vapor at 100 kPa is heated at constant pressure until the temperature reaches 200 C Calculate the work done by the steam during this process Use steam tables The work done by the steam is

You drop an ice cube into an insulated container full of water and wait for the ice cube to completely melt The ice cube initially has a mass of 90 0 g and a temperature of 0 C The water before the ice cube is added has a mass of 760 g and an initial temperature of 24 0 C What is the final temperature in C of the mixture Assume no energy is lost to the walls of the container or to the environment C

MY NOTES ASK YOUR TEACH a A tank contains one mole of carbon dioxide gas at a pressure of 6 70 atm and a temperature of 29 0 C The tank which has a fixed volume is heated until the pressure inside triples What is the final temperature of the gas C b A cylinder with a moveable piston contains one mole of carbon dioxide again at a pressure of 6 70 atm and a temperature of 29 0 C Now the cylinder is heated so that both the pressure inside and the volume of the cylinder double What is the final temperature of the gas

An automobile engine provides 525 Joules of work to push the pistons In this process the internal energy changes by 2896 Joules Calculate q Use the References to access important values if needed for this q for the engine The represents the amount of heat that must be carried away by the cooling system Joules

Is the boundary work associated with constant volume systems always zero Yes or No Yes No T E NTZACHARS