1. One mole of an ideal diatomic gas undergoes undergoes a transition from A to B along a path AB as shown in the figure.
   
   The change in internal energy of the gas during the transition is:

1. 1. – 20 kJ

   
   
   

   2. 20 J

   
   
   

   3. –12 kJ

   
   
   

   4. 20 kJ

   
   
   

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1. View Hint View Answer Discuss in Forum

   Change in internal energy from A → B
   

   ∆U =	f	nR∆T =	f	nR (Tf – Ti)	5	{PfVf – PiVi}
   	2		2		2

   
   (As gas is diatomic ∴ f = 5)
   

   =	5	{2 × 10³ × 6 – 5 × 10³ × 4}
   	2

   
   

   =	5	{12 - 20} × 10³J = 5 × (-4) × 10³J
   	2

   
   ∆U = - 20KJ

   Correct Option: A

   Change in internal energy from A → B
   

   ∆U =	f	nR∆T =	f	nR (Tf – Ti)	5	{PfVf – PiVi}
   	2		2		2

   
   (As gas is diatomic ∴ f = 5)
   

   =	5	{2 × 10³ × 6 – 5 × 10³ × 4}
   	2

   
   

   =	5	{12 - 20} × 10³J = 5 × (-4) × 10³J
   	2

   
   ∆U = - 20KJ

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2. A gas mixture consists of 2 moles of O₂ and 4 moles of Ar at temperature T. Neglecting all vibrational modes, the total internal energy of the system is :-

1. 1. 15 RT

   
   
   

   2. 9 RT

   
   
   

   3. 11 RT

   
   
   

   4. 4 RT

   
   
   

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1. View Hint View Answer Discuss in Forum

   Internal energy of the system is given by
   

   U =	f	nRT
   	2

   
   Degree of freedom
   F_diatomic = 5
   f_monoatomic = 3
   and, number of moles
   n(O₂) = 2
   n(Ar) = 4
   

   Utotal =	5	(2)TR +	3	(4)TR = 11RT
   	2		2

   Correct Option: C

   Internal energy of the system is given by
   

   U =	f	nRT
   	2

   
   Degree of freedom
   F_diatomic = 5
   f_monoatomic = 3
   and, number of moles
   n(O₂) = 2
   n(Ar) = 4
   

   Utotal =	5	(2)TR +	3	(4)TR = 11RT
   	2		2

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3. Two containers A and B are partly filled with water and closed. The volume of A is twice that of B and it contains half the amount of water in B. If both are at the same temperature, the water vapour in the containers will have pressure in the ratio of

1. 1. 1 : 2

   
   
   

   2. 1 : 1

   
   
   

   3. 2 : 1

   
   
   

   4. 4 : 1

   
   
   

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1. View Hint View Answer Discuss in Forum

   Vapour pressure  does not depend on the amount of substance. It depends on the temperature alone.

   Correct Option: B

   Vapour pressure  does not depend on the amount of substance. It depends on the temperature alone.

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4. According to kinetic theory of gases, at absolute zero temperature

1. 1. water freezes

   
   
   

   2. liquid helium freezes

   
   
   

   3. molecular motion stops

   
   
   

   4. liquid hydrogen freezes

   
   
   

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1. View Hint View Answer Discuss in Forum

   NA

   Correct Option: C

   NA

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5. In the given (V – T) diagram, what is the relation between pressure P₁ and P₂ ?
   

1. 1. P₂ > P₁

   
   
   

   2. P₂ < P₁

   
   
   

   3. Cannot be predicted

   
   
   

   4. P₂ = P₁

   
   
   

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1. View Hint View Answer Discuss in Forum

   P₁ > P₂
   
   As V = constant ⇒ P∝ T
   Hence from V–T graph P₁ > P₂

   Correct Option: B

   P₁ > P₂
   
   As V = constant ⇒ P∝ T
   Hence from V–T graph P₁ > P₂

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