Thermodynamics Questions and Answers

where y is the ratio of specific heats dv V dv V 1 dV Y V Y V dv

If a moles of a monoatomic gas are mixed with B moles of a polyatomic gas and mixture behaves like diatomic gas then neglect the vibrational mode of freedom 1 2a B 3 38 2 28 4 3x 8

A closed container has two non reactive gases neon and oxygen with their partial pressure ratio 3 2 If the atomic mass of Ne 20 2 u and molecular mass of O is 32 u then the ratio of their mass density is approximately 1 0 947 2 1 236 3 4 218 4 6 329

Two glass bulbs of equal volume are connected by a narrow tube and filled with a gas at temperature 27 C and pressure 77 cm of Hg One of the bulbs is now kept at temperature 127 C then new pressure inside the bulb is 1 80 cm of Hg 2 76 cm of Hg 3 88 cm of Hg 4 90 cm of Hg

7 If the temperature of 4kg mass of a material of specific heat capacity 300J kg C rises from 20 C to 30 C Find the

12 22 A closed system undergoes a change of state by process 1 2 for which Q12 10 J and W 2 5J The system is now returned to its initial state by a different path 2 1 for which Q2 1 is 3 J The work done by the gas in the process 2 lis a 8 J b zero c 2 J d 5 J clow

1 g of water at 373 K is converted into steam at the same temperature at normal pressure The volume of 1 cm of water becomes 1671 cm on boiling Calculate the change in the internal energy of the system if the heat of vaporisation is 540 cal g

D 8 A black body initially at temperature T cools to temperature T 2 in time At in surrounding which is nea absolute zero It will cool further to a temperature T 4 in additional time A 8At B 7At C 94t D None

Following are the observations made for a black at 3000 K Amount of energy emitted per second 553 O U U U Range of wavelength of radiation 490 nm to 500 nm 990 nm to 1000 nm 1490 nm to 1500 nm When s constant 3x10 nmK Mark the correct option

1 23 In the arrangement as shown in the figure th stepped steel bar ABC is loaded by a load P Th material has Young s modulus E 200 GPa an the two portions AB and BC have area of cros section 1 cm and 2 cm respectively The magnitude of load Prequired to fill up the gap of 0 75 mm is A a 10 kN B P 1m 1m Gap 0 75 mm b 15 kN

An ideal gas is taken through the cycle A B C A 2 V m 1 B A 10 P N m as shown in the figure If the net heat supplied to the gas in the cycle is 5 J the work done by the gas in the process C A is 1 5 J 3 15 J 2 10 J 4 20 J

A sample of ideal gas y 1 4 is heated at constant pressure If an amount of 100 J heat is supplied to the gas the work done by the gas is 1 42 12 J 2 28 57 J 3 36 23 J 4 56 28 J

42 A cyclic process ABCDA is shown in the p V diagram Which of the following curves represent the same process a c P B DC B C T b d 11 P P PA A B P D A D B C B C D T V Cos 7

In the P V diagram shown in figure ABC is a semicircle P atm 3 B T atm L 2 C A V L 1 2 The work done in the process ABC is T 1 zero 3 2 atm L 2 4 4 atm L

1 During adiabatic process pressure P versus density p equation is 1 PpY constant 3 PYp 1 Y constant 2 PpY constant 4 p pY constant

28 19 g of water at 30 C and 5 g of ice at 20 C are mixed together in a calorimeter What is the final temperature of the mixture Given specific heat of ice 0 5 cal g C and latent heat of fusion of ice 80 cal g 1 or d 10 C

A thermodynamic system undergoes cyclic process 3 PA Po Vo 2 3Po 2Po Po C mro N 11 11 AB Vo B D 2V0 ABCD as shown in figure The work done by the system is 1 Povo 2 2P Vo V 4 zero

A diatomic gas of molecular mass 30 g mol is filled in a rigid container at temperature 20 C Container is fixed with a moving trolley whose velocity is 60 m s If trolley suddenly stops then the rise in temperature of the gas is R universal gas constant A t 1 112 C 5R 3 108 C 2 5R 96 C X

Example 16 13 5 g of water at 30 C and 5 g of ice at 20 C are mixed together in a calorimeter Find the final temperature of mixture Water equivalent of calorimeter is negligible specific heat of ice 0 5 cal g C and latent heat of ice 80 cal g 1 Sal In this 2000

Pressure versus tempeature graph of an ideal gas is as shown in figure Density of the gas at point A is Po Density at B will be PA 3 1 Po 4 4 3 3P 0 Por B To 2To T 2 3 2 Po 4 2po

cyclic process 1 2 3 4 1 is depicted on V T diagram The p T diagram and p V diagrams for this cyclic process are given below Select the incorrect choices a c p P 4 2 V 3 2 1 3 4 T 2 3 b P T 2 3 d None of these 4 T

The value of Cp Cy 1 00 R for a gas in state A and denote Cp Cv 1 06 R in another state If pA and PB PA the pressure and TA and Tg the temperatures in the two TB states then 1 PA PB TA TB 3 PA PRITA T 2 PA PB TA TB 4 PA PB3 TA TB

Illustration 3 Two gases occupy two containers A and B The gas in A of volume 0 13 m3 exerts a pressure of 1 40 M Pa The gas in B of volume 0 15 m exerts a pressure of 0 70 MPa The two containers are united by a tube of negligible volume and the gases are allowed to intermingle Then if the temperature remains constant the final pressure in the container will be in MPa

A gas undergoes a change of state from A to B via two paths path 1 and path 2 as shown in figure Ratio of molar heat capacities in path 1 and path 2 is 1 1 PA A 2 1 B V 2 1

233 P T curve of a cyclic process is shown If number o moles of the gas are n the work done by the gas in the given process is P P2 P T2 B A T TA a nR T T3 T4 T2 D T3 C T b nR T T3 T4 T

12 n moles of an ideal gas undergoes a process A to B as shown Maximum temperature of the gas during the process is 1 3PV nR A 3P Po A I Vo B I 3V 2 V 4P V nR

6 The relation between internal energy U pressure P and volume V of a gas in an adiabatic process is U a bPV where a and b are constants What is the effective value of adiabatic constant y 1 a 2 b 1 h 3 a 1 a b pla

4 Two moles of an ideal TA mono atomic gas undergo a cyclic process as shown in the figure The temperatures in different states are given as 6T 3T 2T4 T3 1800 K Determine the work done by the gas during the cycle 2 www 3

An ideal monatomic gas undergoes expansion according to law P aV where a is a constant Molar heat capacity of the gas in the process is 1 3 R 2 3 2 R 2 4 R 2 3R

c 9000 J d 9800 J 74 Six moles of an ideal gas performs a cycle shown in figure If the temperatures are T 600 K T 800 K Tc 2200 K and T 1200 K the work done per cycle is approximately b 30 kJ B c 40 kJ T T d 60 kJ

shown in the figure PA 3 2 V gas is 1 The temperature of the gas increases from 1 to 2 2 The temperature of the gas decreases from 1 to 2 3 The temperature of the gas decrease first upto a certain point 3 and then increases to 2 4 The temperature of the gas increases first upto a certain point 3 and then decreases to 2

Mixture enclosed in a vessel of volume V 5 consists of 1 mole of a gas A with y 3 7 5 gas with y at a temperature T The relative molar masses of the gases A and B are 4 and 32 respectively The gases do not react and are ideal 2 2 and another They follow the equation PV19 13 constant in adiabatic process The number of moles of the gas B in the mixture is 1 1 3 3 4 1 5

Illustration 11 Two gram mole of a gas which are kept at constant temperature of 0 C are compressed from 4 liter to 1 liter The work done will be

Illustration 9 5 gm air is heated from 4 C to 6 C If the specific heat of air at constant volume is 0 172 cal gm C then increase in the internal energy of air will be

Illustration 13 One liter of air at NTP is suddenly compressed to 1 c c the final pressure will be

Illustration 8 A gas whose y 4 3 is heated at constant pressure How much percent of given heat is used in external work done

1 10 gm of ice at 0 C is kept in a calorimeter of water equivalent 10 gm How much heat should be supplied to the apparatus to evaporate the water R thus formed Neglect loss of heat 1 6200 cal 2 7200 cal 3 13600 cal 4 8200 cal

The graph shown in the figure represents energy density Ex versus for three sources sun welding arc tungsten filament A 1 Tungsten 2 Welding arc 3 Sun B 1 Sun 2 Tungsten 3 Welding arc C 1 Sun 2 Welding arc 3 Tungsten D 1 Welding arc 2 Sun 3 Tungsten Ex 3

In a dark room with ambient temperature To a black body is kept at a temperature T Keeping the temperature of the black body constant at T sunrays are allowed to fall on the black bod 2006 through a hole in the roof of the dark room Assuming that there is no change in the ambien temperature of the room which of the following statement s is are correct A The quantity of radiation absorbed by the black body in unit time will increase B Since emissivity absorptivity hence the quantity of radiation emitted by black body in uni time will increase C Black body radiates more energy in unit time in the visible spectrum D The reflected energy in unit time by the black body remains same 2005

The room heater can provide only 16 C in the room when the temperature outside is 20 C It is not wa and comfortable that is why the electric stove with power of 1 kW is also plugged in Together these t devices maintain the room temperature of 22 C Determine the thermal power of the heater A 3 kW D 6kW B 4 kW C 5 kW

When 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 B 2 81 x 10 m D 1 40 10 0 m

An ideal gas undergoes a quasi static reversible process in which its molar heat capacity C remains constant If during this process the relation of pressure P and volume V is given by PV constant then n is given by Here Cp and Cy are molar specific heat at constant pressure and constant volume respectively 2016 1 n C Cp C Cv C Cv C Cp 3 n 2 n 4 n Cp C C Cv Cp C

The work done by the one mole gas in the cyclic process shown in graph is W Then VE T To A T T T 2 B To W T T 2 2R C To W 2R D To W T T 2R 2

Example 15 36 Temperature of a 5 mole of hydrogen gas decreases by 260 K while expanded through adiabatic process Find the work done by the gas What is the change in internal energy of the gas

The specific heat of alcohol is about half that of water Suppose you have identical masses of alcohol and water The alcohol is initially at temperature TA The water is initially at a different temperature Tw Now the two fluids are mixed in the same container and allowed to come into thermal equilibrium with no loss of heat to the surroundings The final temperature of the mixture will be A closer to T than Tw C exactly halfway between T and Tw A B closer to Tw than TA W D dependent on the volume of alcohol used

Como f 1 10 g of ice at 0 C is kept in a calorimeter of water equivalent 10 g How much heat should be supplied to the apparatus to evaporate the water thus formed Neglect loss of heat sof 2 7200 cal 4 8200 cal 1 6200 cal 201 3 13600 cal

The change in entropy of 1 kg of nitrogen gas in an isobaric process when its temperature changes from 400 K to 800 K is 1 720 J K 3 309 J K 2 420 J K 4 720 cal C

An ideal diatomic gas undergoes a thermodynamic process as shown on indicator P V diagram The heat input during process a to b is PA AP 2Pa 1 12 PV 2 45 PV 3 57 Povo b V 5V V 5

27 A monatomic ideal gas undergoes thermodynamic process as shown in the figure The molar specific heat of the process is 1 R 3 2 3 75 R VA T 2 R 2 a 4 2R

2 A reversible engine absorbs 600 J of heat from source at 627 C and rejects some heat to the sim at 27 C The heat rejected to the sink is 1 500 J 2 400 J 6274273 3 300 J 4 200 J