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question_answer1) Mention the different ways of increasing the number of molecular collisions per unit time in a gas.
question_answer2) What is an ideal gas? Give its main characteristics.
question_answer3) Fig. shows the variation of the product PV with respect to the pressure (P) of given masses of three gases. A, B and C. The temperature is kept constant. State with proper arguments which of these gases is ideal.
question_answer4) Why do the gases at low temperature and high pressure show large deviations from ideal behaviour?
question_answer5) On reducing the volume of a gas at constant temperature, the pressure of the gas increases. Explain it on the basis of kinetic theory.
question_answer6) When an automobile travels for a long distance, the air pressure in the tyres increases slightly. Why?
question_answer7) When a gas is heated, its temperature increases. Explain it on the basis of kinetic theory of gases.
question_answer8) In the upper part of the atmosphere the kinetic temperature of air is of the order of\[\mathbf{1000}\text{ }\mathbf{K}\], event then one feels severe cold there. Why?
question_answer9) In the kinetic theory of gases, why do we not take into account the changes in gravitational potential energy of the molecule?
question_answer10) What type of motion is associated with the molecules of a gas?
question_answer11) Although the root-mean-square speed of gas molecules is of the order of the speed of sound in that gas, yet on opening a bottle of ammonia in one corner of a room its smell takes time in reaching the other corner. Why?
question_answer12) On which factors does the average kinetic energy of gas molecules depend: Nature of the gas, temperature, volume?
question_answer13) What do you mean by the r. m. s. speed of the molecules of a gas? Is r. m. s. speed same as the average speed?
question_answer14) The ratio of vapour densities of two gases at the same temperature is 8:9. Compare the r. m. s. velocities of their molecules.
question_answer15) What is the average velocity of the molecules of an ideal gas?
question_answer16) Given a sample of \[\mathbf{1}\text{ }\mathbf{c}{{\mathbf{m}}^{\mathbf{3}}}\] of hydrogen and\[\mathbf{1}\text{ }\mathbf{c}{{\mathbf{m}}^{\mathbf{3}}}\]of oxygen both at S.T.P. Which sample has a larger number of molecules?
question_answer17) At what temperature does all molecular motion cease? Explain. Or Molecular motion ceases at zero kelvin. Explain.
question_answer18) Why temperature less than absolute zero is not possible?
question_answer19) For an ideal gas, the internal energy can only be translational kinetic energy. Explain.
question_answer20) At a given temperature, equal masses of monoatomic and diatomic gases are supplied equal quantities of heat. Which of the two gases will suffer a larger temperature rise?
question_answer21) Deduce the dimensional formula for R used in the ideal gas equation \[\mathbf{PV}=nRT.\]
question_answer22) A box contains equal number of molecules of hydrogen and oxygen. If there is a fine hole in the box, which gas will leak rapidly? Why?
question_answer23) The mass of a molecule of krypton is 2.25 times the mass of a hydrogen molecule. A mixture of equal masses of these gases is enclosed in a vessel. Calculate at any temperature the ratio of the root mean square velocities of krypton and hydrogen gases.
question_answer24) A sample of an ideal gas occupies a volume V at a pressure P and absolute temperature T. The mass of each molecule is m. If \[{{k}_{B}}\] is the Boltzmann's constant, then write the expression for the density of the gas.
question_answer25) The volume of vessel A is twice the volume of another vessel B, and both of them are filled with the same gas. If the gas in A is at twice the temperature and twice the pressure in comparison to the gas in B, what is the ratio of the gas molecules in A and B?
question_answer26) Two gases, each at temperature T, volume V and pressure P are mixed such that the temperature and volume of the mixture are T and V respectively. What would be the pressure of the mixture? Justify your answer on the basis of kinetic theory.
question_answer27) The total translational kinetic energy of the molecules of a gas having volume V and pressure P is \[\mathbf{500}\text{ }\mathbf{J}\]. What will be the total translational kinetic energy of the molecules of the same gas occupying the same volume V but exerting a pressure 2P?
question_answer28) Write the equation of state for \[\mathbf{16}\text{ }\mathbf{g}\] of\[{{\mathbf{O}}_{\mathbf{2}}}\].
question_answer29) When a gas filled in a closed vessel is heated through\[\mathbf{1}{}^\circ \text{ }\mathbf{C}\], its pressure increases by\[\mathbf{0}.\mathbf{4}%\]. What is the initial temperature of the gas?
question_answer30) A gas in a closed vessel is at the pressure \[{{P}_{0}}\] . If the masses of all the molecules be made half and their speeds be made double, then find the resultant pressure.
question_answer31) What is evaporation?
question_answer32) Why does evaporation cause cooling?
question_answer33) Cooking gas containers are kept in a lorry moving with uniform speed. What will be the effect on temperature of the gas molecules?
question_answer34) Should the specific heat of monoatomic gas be less than, equal to or greater than that of a diatomic gas at room temperature? Justify your answer.
question_answer35) What is Debye temperature?
question_answer36) Equal masses of helium and oxygen gases are given equal quantities of heat. Which gas will undergo a greater temperature rise?
question_answer37) A gas is filled in a cylinder fitted with piston at a constant temperature. Explain on the basis of kinetic theory: (i) The pressure of the gas increases by raising the temperature. (ii) On pulling the piston out, the pressure of the gas decreases.
question_answer38) There are N molecules of a gas in a container. If the number of molecules is increased to 2N, what will be (i) pressure of the gas, (ii) total energy of the gas and (ii) r. m. s. speed of the gas?
question_answer39) Although the velocity of air molecules is nearly \[\mathbf{0}\mathbf{.5 km }{{\mathbf{s}}^{\mathbf{-1}}}\], yet the smell of scent spreads at a much slower rate. Why?
question_answer40) When do the real gases obey more correctly the gas equation: \[PV=nRT\]?
question_answer41) Explain qualitatively how the extent of Brownian motion is affected by the (a) size of the Brownian particle, (b) density of the medium, (c) temperature of the medium, (d) viscosity of the medium?
question_answer42) For Brownian motion of particles of suspensions in liquids, what should be the typical size of suspended particles? Why should not the size of the particles be too small (say of atomic dimensions \[\mathbf{1}{{\mathbf{0}}^{\mathbf{-10}}}\mathbf{m}\] ) or too large (say of the order of \[\mathbf{1m}\])?
question_answer43) What is the simplest evidence in nature that you can think of to suggest that atoms are not point particles?
question_answer44) In an experiment, the specific heats of some inert gases (at ordinary temperatures) are measured to be as follows: Gas Atomic mass \[(u)\] Specific heat (cal\[{{\mathbf{g}}^{\mathbf{-1}}}{{\mathbf{K}}^{\mathbf{-1}}}\]) Helium 4.00 0.748 Neon 20.18 0.147 Argon 39.94 0.0760 Krypton 83.80 0.0358 Xenon 131.3 0.0226 Try to discover a regularity in the data and explain it on the basis of kinetic energy.
question_answer45) What is meant by molar specific heat of a gas? The molar specific heat of hydrogen \[{{\mathbf{H}}_{\mathbf{2}}}\] is about \[\frac{\mathbf{5}}{\mathbf{2}}\mathbf{R}\]in the temperature range of about \[\mathbf{250}\text{ }\mathbf{K}\] to\[\mathbf{750}\text{ }\mathbf{K}\]. At lower temperatures, molar specific heat of hydrogen decreases to the value typical of monoatomic gases: \[\frac{\mathbf{3}}{\mathbf{2}}\mathbf{R}.\] At higher temperatures, it tends to the value \[\frac{7}{2}\] \[R\]. What do you think is happening?
question_answer46) (a) When a molecule (or an elastic ball) hits a (massive) wall, it rebounds with the same speed. When a ball hits a massive bat held firmly, the same thing happens. However, when the bat is moving towards the ball/the ball rebounds with a different speed. Does the ball move faster or slower? (b) When gas in a cylinder is compressed by pushing in a piston, its temperature rises. Guess at an explanation of this in terms of kinetic theory using (a) above. (c) What happens when a compressed gas pushes a piston out and expands? What would you observe? (d) Sachin Tendulkar uses a heavy cricket bat while playing. Does it help him in any way?
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