P0IITU10 - Heat & thermodynamics qns asked in IIT

P0IITU10 - Heat & thermodynamics qns asked in IIT -...

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QUEST TUTORIALS Head Office : E-16/289, Sector-8, Rohini, New Delhi, Ph. 65395439 HEAT & THERMODYNAMICS PROBLEMS ASKED IN JEE & REE Q 1. State whether True of False : (with reason) [ JEE '87, 2 + 2 ] (a) At a given temperature, the specific heat of a gas at constant pressure is always greater than its specific heat at constant volumes . (b) The root mean square (rms) speed of oxygen molecules (O 2 ) at a certain temperature T (degree absolute) is V . If temperature is doubled and oxygen gas dissociates into oxygen atoms, the rms speed is unchanged . Q 2. An ideal gas has a specific heat at constant pressure C p = 5 2 R . The gas is kept in a closed vessel of volume 0.0083 m 3 at 6 N/m 2 . An amount of 2.49 x 10 4 Joules of heat energy is supplied to the gas . Calculate the final [ JEE '87, 7 ] Q 3. A container is divided into two equal portions . One portion contains an ideal gas at pressure P and temperature T, while the other portion has a perfect vaccum . If a hole is opened between the two portions, find the change in energy and change in temperature of the gas . [ REE '87, 3 ] Q 4. 2 M 3 volume of gas at a pressure of 4 x 10 5 Nm - 2 is compressed adiabatically so that the volume becomes 0.5 M 3 . Find the new pressure that would result, if the compression was isothermal . Calculate work done in each process . [ γ = 1.4 ] [ REE '87, 7 ] Q 5. Two moles of helium gas γ = 5 3 are initially at temperature 27º C and occupy a volume of 20 litres . The gas is first expanded at constant pressure unitl the volume is doubled . Then it undergoes an adiabtic change until the temperature returns to its initial value . (i) sketch the process on a p-V diagram . (ii) what are final volume and pressure of the gas ? (iii) what is the work done by the gas ? [ JEE '88, 6 ] Q 6. State whether True or False :(give reasons) [ JEE '88, 2 ] 2 spheres of the same material have radii 1 m and temperature 4000º K respectively . The energy radiated per second by the first sphere is greater than that by the second . Q 7. In a certain region of space there are only 5 molecules per cm 3 on an average . The temperature there is 3º K . What is the average pressure of this very dilute gas ? [ REE '88, 5 ] Q 8. A 50 gm lead bullet, specific heat 0.02 is initially at 30º C . It is fired vertically upwards C. How much ice is melted . Assume that all energy is spent in melting only . [ latent heat of ice = 80 cal/gm ] [ REE '88, 5 ] Q 9. hydrogen atom in its ground state is excited by means of a monochromatic radiation of wavelength 970.6 Aº . How many different wavelengths are possible in the resulting emission spectrum ? Find the longest wavelength amongst these . [ REE '89, 7 ]
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P0IITU10 - Heat & thermodynamics qns asked in IIT -...

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