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Q. No.When an ideal gas is compressed adiabatically, its temperature rises: the molecules on an average have more kinetic energy than before. The kinetic energy increases:
| 1. | because of collisions with moving parts of the wall only. |
| 2. | because of collisions with the entire wall. |
| 3. | because the molecules get accelerated in their motion inside the volume. |
| 4. | because of the redistribution of energy amongst the molecules. |
A cubic vessel (with faces horizontal + vertical) contains an ideal gas at NTP. The vessel is being carried by a rocket which is moving at a speed of in the vertical direction. The pressure of the gas inside the vessel as observed by us on the ground:
| 1. | remains the same because \(500\) \(\mathrm{ms^{-1}}\) is very much smaller than \(v_{rms}\) of the gas. |
| 2. | remains the same because the motion of the vessel as a whole does not affect the relative motion of the gas molecules and the walls. |
| 3. | will increase by a factor equal to \(\Big(\frac{v_{rms}^2+(500)^2}{v_{rms}^2}\Big)\)where \(v_{rms}^2\) was the original mean square velocity of the gas. |
| 4. | will be different on the top wall and bottom wall of the vessel. |
1 mole of an ideal gas is contained in a cubical volume V, ABCDEFGH at 300 K (figure). One face of the cube (EFGH) is made up of a material which totally absorbs any gas molecule incident on it. At any given time:
| 1. | the pressure on EFGH would be zero. |
| 2. | the pressure on all the faces will be equal. |
| 3. | the pressure on EFGH would be double the pressure on ABCD. |
| 4. | the pressure on EFGH would be half that on ABCD. |
ABCDEFGH is a hollow cube made of an insulator (figure). Face ABCD has a positive charge on it. Inside the cube, we have ionised hydrogen. The usual kinetic theory expression for pressure:
| a. | will be valid. |
| b. | will not be valid, since the ions would experience forces other than due to collisions with the walls. |
| c. | will not be valid, since collisions with walls would not be elastic. |
| d. | will not be valid because isotropy is lost. |
Choose the correct alternatives:
1. only (a)
2. (b, c)
3. (b, d)
4. (c, d)
Diatomic molecules like hydrogen have energies due to both translational as well as rotational motion. From the equation in kinetic theory, \(PV = \frac{2}{3}E\) \(E\) is:
| 1. | the total energy per unit volume. |
| 2. | only the translational part of energy because rotational energy is very small compared to translational energy. |
| 3. | only the translational part of the energy because during collisions with the wall, pressure relates to change in linear momentum. |
| 4. | the translational part of the energy because rotational energies of molecules can be of either sign and its average over all the molecules is zero. |
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