JEE Mains Previous Years Questions with Solutions

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1

AIEEE 2005

Which one of the following statements is NOT true about the effect of an increase in temperature on the distribution of molecular speeds in a gas?
A
The most probable speed increases
B
The fraction of the molecules with the most probable speed increases
C
D
The area under the distribution curve remains the same as under the lower temperature

Explanation

Distribution of molecular velocities at two different temperature is given shown below.

NOTE : At higher temperature more molecules have higher velocities and less molecules have lower velocities.

As evident from fig. thus it is clear that With the increase in temperature the most probable velocity increase but the fraction of such molecules decreases.
2

AIEEE 2004

In Van der Waals equation of state of the gas law, the constant ‘b’ is a measure of
A
intermolecular repulsions
B
intermolecular collisions per unit volume
C
Volume occupied by the molecules
D
intermolecular attraction

Explanation

In van der Waals equation $'b'$ is for volume correction.
3

AIEEE 2004

As the temperature is raised from 20°C to 40°C, the average kinetic energy of neon atoms changes by a factor of which of the following?
A
1/2
B
2
C
$313\over293$
D
$\sqrt{313\over293}$

Explanation

${{K.E\,\,of\,\,neon\,\,at\,\,{{40}^ \circ }C} \over {K.E\,\,of\,\,neon\,\,at\,\,{{20}^ \circ }C}}$

$= {{{3 \over 2}K \times 313} \over {{3 \over 2}K \times 293}}$

$= {{313} \over {293}}$
4

AIEEE 2003

According to the kinetic theory of gases, in an ideal gas, between two successive collisions of a gas molecule travels
A
in a wavy path
B
in a straight line path
C
with an accelerated velocity
D
in a circular path

Explanation

According to kinetic theory the gas molecules are in a state of constant rapid motion in all possible directions colloiding in a random manner with one another and with the walls of the container and between two successive collisions molecules travel in a straight line path but show haphazard motion due to collisions.