Average and Root Mean Square Speeds of the Gas Molecules

Author:Chittaranjan Dasgupta & Asok Kumar Das
11th West Bengal Board
IMPORTANT

Important Questions on Average and Root Mean Square Speeds of the Gas Molecules

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The rms speed of an ideal gas is c. The volume of the gas is doubled keeping its temperature unchanged. The rms speed will now be

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The ratio of the most probable velocity cm and rms velocity crms of the molecules of a given gas at a given temperature is

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There is a mixture of hydrogen and oxygen in a vessel. The rms velocity of oxygen molecules is

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The average velocity of a gas molecule is c¯, rms velocity crms and the most probable velocity, cm. Then

HARD
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Calculate the most probable speed, mean speed and rootmean-square speed for nitrogen at 300 K.

HARD
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In a closed vessel one gm mole of nitrogen is kept at a temperature of 300 K. What is the amount of heat required to raise the temperature of the gas, so that the r.m.s. Speed of molecules becomes 3 Times its initial value. Given: R=2 cal/k-mol.

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2 gm mol of helium having r.m.s. speed of molecules 1000 ms-1 and 0.5 gm mol of nitrogen having r.m.s. speed 3000 ms-1 are mixed in thermally insulated container. What are the r.m.s. speeds of helium and nitrogen molecules after equilibrium is reached?

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Kinetic temperature of small particle is the temperature of a gas at equilibrium, whose most probable speed is the speed of the particle. Find the kinetic temperature of a proton of energy 1 mev and that of a ball of mass 250 gm moving with a velocity of 10 ms-1.

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The average translational energy and the rms speed of molecules in a gas at 300 K are 6.21×10-21 J and 484 m s-1 respectively. What are the corresponding values at 600 K (assuming ideal gas behaviour)?

MEDIUM
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Calculate the r.m.s. speed of smoke particles of mass 5×10-17 kgin Brownian motion in air at NTP. Given : Boltzmann constant k=1.38×10-23JK-1.

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Calcultate the density of an ideal gas at S.T.P. if r.m.s velocity of molecules be 0.5 km/s. What will be the density of the gas at 21°C, the pressure remaining the same? (Assume 1 standard atmosphere =105 N/m2).

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Calculate the total K.E. of the molecules in 16 g of O2 gas at 27°CR=8.31 joule C-1 mole-1.

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At 0°C and 10-2 Atmospheric pressure, the density of a gas is 1.24×10-2 kg m-3. Find the r m s speed of the gas molecules and its molecular mass.

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Given that the gas constant R=8.3 joule per °C and the atomic mass of chlorine is 35.5, find the rms speed of chlorine molecules at 0°C.

MEDIUM
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At what temperature is the rms speed of hydrogen molecule equal to that of a carbon dioxide molecule at 57°C? A carbon dioxide molecule is about 22 times heavier than a hydrogen molecule.

HARD
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What is most probable speed of the gas molecules? Compare its value with the mean and r.m.s. speeds of the gas molecules.

MEDIUM
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The earth has an atmosphere of different gases like nitrogen, oxygen etc. But moon has no atmosphere Explain.

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The average velocity of the molecules of a gas must be zero if the gas as a whole and the container are not in translational motion. How is it possible that the average speed of molecules is not zero?

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What will be the percentage change in the rms velocity of gas molecules when its pressure is doubled keeping temperature constant.

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Show the expressions for most probable speed, mean speed and r.m.s. speed and find their relative magnitudes.