A one litre flask contains 2 . 5 × 10 25 molecules of a gas each of mass 5 × 10 - 28 kg and having its rms speed 150 m s - 1 . Find the pressure of the gas.

Using kinetic gas equation The pressure of the gas. P = 1 3 mnc 2 V Given: , V = 1 litre = 1000 mL = 1000 cm 3 ; n = 2 . 5 × 10 25 ; m = 5 × 10 - 28 Kg = 5000 × 10 - 28 = 5 × 10 - 25 g and c = 150 m s - 1 . Substituting the values in the above equation, P = 1 3 × 5 × 10 - 25 × 2 . 5 × 10 - 25 150 2 1000 = 281250 3 × 1000 = 281250 3000 = 9 . 735 × 10 4 Nm - 2 So, the pressure of the gas = 9 . 735 × 10 4 Nm - 2

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.

We know that V rms = 3 P ρ Where P = The Pressure of the gas and ρ = Density of the gas. Given, P = 1 . 24 × 10 - 2 kg m - 3 , ρ = 10 - 2 Putting the value in the formula we get V rms = 3 × 1 . 24 × 10 - 2 10 - 2 = 495 ms - 1 To find Molecular mass M from ρ = PM RT With T = 273 K ∴ M = ρRT P = ( 0 . 0124 kg / m 3 ) ( 8 . 31 J / mol . K ) ( 273 K ) 1 . 01 × 10 3 = 0 . 0279 kg / mol = 27 . 9 g / mol .

E M B I B E

A Text Book of PHYSICS PART I : CLASS 11>Chapter 20 - Kinetic Theory of Gases>EXERCISE>Q 14

HARD

11th West Bengal Board

IMPORTANT

Earn 100

State the characteristics of Brownian motion.

Important Questions on Kinetic Theory of Gases

MEDIUM

11th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART I : CLASS 11>Chapter 20 - Kinetic Theory of Gases>EXERCISE>Q 15

How Brownian motion could be explained on the basis of thermal motion of the molecules?

HARD

11th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART I : CLASS 11>Chapter 20 - Kinetic Theory of Gases>EXERCISE>Q 16

What is critical temperature of a gas? What are critical points, critical pressure and critical volume?

MEDIUM

11th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART I : CLASS 11>Chapter 20 - Kinetic Theory of Gases>EXERCISE>Q 17

What modifications in the basic assumptions of kinetic theory was introduced by Van-der-Waals? Explain qualitatively how he arrived at the modified equation.

HARD

11th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART I : CLASS 11>Chapter 20 - Kinetic Theory of Gases>EXERCISE>Q 18

Write down the Van-der-Waals equation for real gases. Explain the terms of the equation. Explain why this equation is to be regarded as an empirical equation.

HARD

11th West Bengal Board

IMPORTANT

A Text Book of PHYSICS PART I : CLASS 11>Chapter 20 - Kinetic Theory of Gases>EXERCISE>Q 1

A one litre flask contains