Tag: kinetic theory of gases

Questions Related to kinetic theory of gases

The gas, which is present the most in air, is___

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. oxygen

  2. nitrogen

  3. carbon dioxide

  4. water vapour

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Correct Option: B
Explanation:

1) Nitrogen $-78$%

2) Oxygen $-21$%
3) Inert Nobel gases $-0.9$%
4) Several trace gases $-0.1$%
The above list the different number of gases in descending order. As per the list clearly Nitrogen is the gas present in most air.

Heat is associated with 

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. kinetic energy of random motion of molecules

  2. kinetic energy of orderly motion of molecules

  3. total kinetic energy of random and orderly motion of molecules

  4. kinetic energy of random motion in some cases and kinetic energy orderly motion in other.

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Correct Option: A
Explanation:

Heating up a substance excites the molecules of that substance making  the molecules moves vigorously thus giving velocity to the molecules and we know kinetic energy of a body is by the virtue of its motion.       

The kinetic energy of translation of $20gm$ of oxygen at $47^oC$ is (molecule wt. of oxygen is $32gm/mol $and $R=8.3J/mol/K$)

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  1. 2490 joules

  2. 2490 ergs

  3. 830 joules

  4. 124.5 joules

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Correct Option: A

What is an ideal gas?

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. One that consists of molecules

  2. A gas satisfying the assumptions of kinetic theory

  3. A gas having Maxwellian distribution of speed

  4. A gas consisting of massless particles

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Correct Option: B
Explanation:

An ideal gas is a gas which satisfying the assumptions of the kinetic energy.

Statement 1: The internal energy of a perfect gas is entirely kinetic and depends only on absolute temperature of the gas and not on its pressure or volume.
Statement 2: A perfect gas is heated keeping pressure constant and later at constant volume. For the same amount of heat the temperature of the gas at constant pressure is lower than that at constant volume.

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. Statement 1 is true, statement 2 is true and statement 2 is correct explanation of statement 1

  2. statement 1 is true, statement 2 is false

  3. Statement 1 is true, Statement 2 is true but Statement 2 is not the correct explanation of Statement 1

  4. Statement 1 is false, Statement 2 is true

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Correct Option: C

A body at a temperature of ${ 727 }^{ \circ  }C$ and having surface area ${ 5cm }^{ 2 }$ , radiated 300J of energy each minute. The emissivity (Given: boltzmann constant=$ 5.67\times { 10 }^{ -8 }{ Wm }^{ -2 }{ K }^{ -4 }$ is

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. e=0.2

  2. e=0.02

  3. e=0.18

  4. e=0.15

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Correct Option: A

The average pressure of an ideal gas is  

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. $\rho = (1/3)\, mn \, V^2 _{av}$

  2. $\rho = (1/2)\, mn \, V _{av}$

  3. $\rho = (1/4)\, mn \, V^2 _{av}$

  4. $\rho = (1/3)\, mn \, V _{av}$

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Correct Option: A

The pressure of air increases by $100mm$ of Hg and the temperature decreases by $1^0C$. The change in the speed of sound in air at STP is

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  1. $61ms^{-1}$

  2. $61mms^{-1}$

  3. $61 cms^{-1}$

  4. $0.61 cms^{-1}$

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Correct Option: D

The equation of state of some gases can be expressed as (p+av2)(v−b)=RT Here p is pressure, v is volume , a,b,R are constants. The dimensions of ′a′ are

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. $ML^{-5}T^{-2}$

  2. $ML^{-1} T^{-2}$

  3. $M^o L^3T^o$

  4. $M^B L^oT^o$

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Correct Option: A
Explanation:

Here $P$ and $a/{ V }^{ 2 }$ are added that means they have same dimensions.

Therefore,
$\left[ { M }^{ 1 }{ L }^{ -1 }{ T }^{ -2 } \right] =\dfrac { a }{ \left[ { M }^{ 0 }{ L }^{ 6 }{ T }^{ 0 } \right]  } $
$a=\dfrac { { M }^{ 1 }{ L }^{ -1 }{ T }^{ -2 } }{ { M }^{ 0 }{ L }^{ 6 }{ T }^{ 0 } } $
$a={ M }^{ 1 }{ L }^{ 5 }{ T }^{ -2 }$

According to kinetic theory of gases,

modelling gases - the kinetic model ideal gases kinetic theory of gases physics

  1. The velocity of molecules decreases for each collision

  2. The pressure exerted by a diatomic gas is proportional to teh mean velocity of the molecule

  3. The K.E of the gas decreases on expansion at constant temperature

  4. The mean translational KE of a diatomic gas increases with increase in absolute temperature

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Correct Option: D
Explanation:

Options:
(A): One can not say velocity of molecule decreases  in each collision.
(B): The pressure exerted by a diatomic gas is proportional to rms speed, not mean speed.
(C): Since temp is constant, KE will be constant.
(D): Mean translational KE is proportional to temp, hence will increase with increase in absolute temp.