The average kinetic energy of a helium atom at is: [MP PMT 2004]
1. Less than 1 eV
2. A few KeV
3. 50-60 eV
4. 13.6 eV
The mean translational kinetic energy of a perfect gas molecule at the temperature T Kelvin is:
1.
2. kT
3.
4. 2 kT
One liter of gas A and two liters of gas B, both having the same temperature 100C and the same pressure 2.5 bar will have the ratio of average kinetic energies of their molecules as:
1. 1:1
2. 1:2
3. 1:4
4. 4:1
An ideal gas is filled in a vessel, then
1. If it is placed inside a moving train, its temperature increases
2. Its centre of mass moves randomly
3. Its temperature remains constant in a moving car
4. None of these
The root mean square speed of oxygen molecules (O2) at a certain absolute temperature is v. If the temperature is doubled and oxygen gas dissociates into oxygen atom, the rms speed would be :
1.
2.
3.
4.
If P is the pressure of the gas then the KE per unit volume of the gas is:
1.
2.
3.
4.
For an ideal gas V-T curves at constant pressure and are shown in figure. From the figure
1.
2.
3.
4.
A gas mixture consist of 2 moles of and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is:
(1)4RT
(2) 15RT
(3)9RT
(4)11RT
The mean free path of gas A, with molecular diameter equal to 4 Å, contained in a vessel, at a pressure of torr, is 6990 cm. The vessel is evacuated and then filled with gas B, with molecular diameter, equal to 2 Å, at a pressure of torr, the temperature remaining the same. The mean free path of gas B will be
(A) 28 cm
(B) 280 cm
(C) 7 cm
(D) 14 cm
The mean free path of gas molecules depends on (d = molecular diameter)
1.
2.
3.
4.
A gas at 27°C temperature and 30 atmospheric pressure is allowed to expand to the atmospheric pressure. If the volume becomes 10 times its initial volume, then the final temperature becomes
1. 100°C
2. 173°C
3. 273°C
4. – 173°C
The equation of state for 5 g of oxygen at a pressure P and temperature T, when occupying a volume V, will be
1.
2.
3.
4.
(where R is the gas constant)
At a given volume and temperature, the pressure of a gas :
1. Varies inversely as its mass
2. Varies inversely as the square of its mass
3. Varies linearly as its mass
4. Is independent of its mass
Two thermally insulated vessels 1 and 2 are filled with air at temperatures volume and pressure respectively. If the valve joining the two vessels is opened, the temperature inside the vessel at equilibrium will be
1.
2.
3.
4.
In Vander Waal’s equation, a and b represent
1. Both a and b represent correction in volume
2. Both a and b represent adhesive force between molecules
3. a represents adhesive force between molecules and b correction in volume
4. a represents correction in volume and b represents adhesive force between molecules
At 0°C the density of a fixed mass of a gas divided by pressure is x. At 100°C, the ratio will be:
1.
2.
3.
4.
If an ideal gas has volume V at 27°C and it is heated at a constant pressure so that its volume becomes 1.5V. Then the value of final temperature will be
1. 600°C
2. 177°C
3. 817°C
4. None of these
In Boyle's law what remains constant :
1.
2.
3.
4.
Equation of gas in terms of pressure (P), absolute temperature (T) and density (d) is :
1.
2.
3.
4.
The respective speeds of the molecules are 1, 2, 3, 4 and 5 km/sec. The ratio of their r.m.s. velocity and the average velocity will be
1.
2.
3.
4.
Two vessels having equal volume contain molecular hydrogen at one atmosphere and helium at two atmospheres respectively. If both samples are at the same temperature, the mean velocity of hydrogen molecules is
1. Equal to that of helium
2. Twice that of helium
3. Half that of helium
4. times that of helium
The temperature of an ideal gas is increased from 120 K to 480 K. If at 120 K, the root mean square velocity of the gas molecules is v, at 480 K it becomes
1. 4v
2. 2v
3. v/2
4. v/4
The value of densities of two diatomic gases at constant temperature and pressure are and then the ratio of the speed of sound in these gases will be :
1.
2.
3.
4.
By what factor the r.m.s. velocity will change, if the temperature is raised from 27°C to 327°C
1.
2.
3.
4.
At a given temperature if is the root mean square velocity of the molecules of a gas and the velocity of sound in it, then these are related as
1.
2.
3.
4.
Let A and B the two gases and given : where T is the temperature and M is molecular mass. If and are the r.m.s. speed, then the ratio will be equal to
1. 2
2. 4
3. 1
4. 0.5
For a gas at a temperature the root-mean-square velocity , the most probable speed , and the average speed obey the relationship
1.
2.
3.
4.
If and denote the root-mean square velocities of molecules of hydrogen, nitrogen and oxygen respectively at a given temperature, then
1.
2.
3.
4.
The r.m.s. speed of a group of 7 gas molecules having speeds is
1.
2.
3.
4.
If the ratio of vapour density for hydrogen and oxygen is , then under constant pressure the ratio of their rms velocities will be
1.
2.
3.
4.
What is the velocity of wave in monoatomic gas having pressure 1 kilopascal and density ?
1.
2.
3. Zero
4. None of these
If the pressure in a closed vessel is reduced by drawing out some gas, the mean free path of the molecules:
1. | decreases |
2. | increases |
3. | remains unchanged |
4. | increases or decreases according to the nature of the gas |
The r.m.s. speed of a certain gas is n at 400K. The temperature at which the r.m.s. speed becomes two times, will be
1. 800 K
2. 1600 K
3. 1200 K
3. None of these
A cubical box with porous walls containing an equal number of and molecules is placed in a large evacuated chamber. The entire system is maintained at constant temperature T. The ratio of of molecules to that of the of molecules, found in the chamber outside the box after a short interval is
1.
2.
3.
4.
Gas at a pressure is contained in a vessel. If the masses of all the molecules are halved and their speeds are doubled, the resulting pressure P will be equal to
1.
2.
3.
4.
Consider a gas with density and as the root mean square velocity of its molecules contained in a volume. If the system moves as whole with velocity v, then the pressure exerted by the gas is
1.
2.
3.
4.
If the mean free path of atoms is doubled , then the pressure of gas will become
1. P/4
2. P/2
3. P/8
4. P
A sealed container with negligible coefficient of volumetric expansion contains helium (a monoatomic gas). When it is heated from 300 K to 600 K, the average K.E. of helium atoms is
1. Halved
2. Unchanged
3. Doubled
4. Increased by factor
The kinetic energy of translation of 20 gm of oxygen at 47°C is (molecular wt. of oxygen is 32 gm/mol and R = 8.3 J/mol/K)
1. 2490 joules
2. 2490 ergs
3. 830 joules
4. 124.5 joules
The kinetic energy of one gram molecules of a gas at standard temperature and pressure:
1.
2.
3.
4.
A vessel is partitioned in two equal halves by a fixed diathermic separator. Two different ideal gases are filled in left (L) and right (R) halves. The rms speed of the molecules in L part is equal to the mean speed of molecules in the R part. Then the ratio of the mass of a molecule in L part to that of a molecule in R part is
1.
2.
3.
4.
A gas mixture consists of 2 moles of Oxygen and 4 moles of Argon at temperature T. Neglecting all vibrational modes, the total internal energy of the system is:
1. 4 RT
2. 15 RT
3. 9 RT
4. 11 RT
A jar contains a gas and few drops of water at T K. The pressure in the jar is 830 mm of mercury. The temperature of jar is reduced by 1%. The saturated vapour pressure of water at the two temperatures are 30 mm and 25 mm of mercury. Then the new pressure in the jar will be
1. 917 mm of Hg
2. 717 mm of Hg
3. 817 mm of Hg
4. None of these
Assertion: At a particular temperature, the value of the mean free path increases with a decrease in pressure.
Reason: All the gas molecules at a particular temperature possess the same speed.
The mean free path () of a gas sample is given by:
1.
2.
3.
4. None of these