Question

a container is filled with 20 moles of an ideal diatomic gas at Absolute Temperature t when heat is supplied to gas temperature remains constant but 8 mole dissociate into atom. heat energy given to gas is

Answer 1

As gas is enclosed in a vessel, so during heating process, volume of the gas remains constant. It means no work is done by the gas  and heat supplied to the gas is used to increase its internal energy only.

Initial internal energy of the gas= 1 = 1 ( 5/2 ).

 after heating, vessel contains (1 − 2) moles of diatomic gas
 Hence the internal energy for the gas, after heating= 
= 2 = (1 − 2 ) ( 5 /2 ) + 22 ( 3 /2 )
= 5 /2 1 () + 1 /2 2 ().

2 − 1 = 1 /2 2 ()
= 1 /2 ∙ 8()
= 4RT

Answer 2

Explanation:

As gas is enclosed in a vessel, so during heating process, volume of the gas remains constant. It means no work is done by the gas  and heat supplied to the gas is used to increase its internal energy only.

Initial internal energy of the gas= 1 = 1 ( 5/2 ).

 after heating, vessel contains (1 − 2) moles of diatomic gas

 Hence the internal energy for the gas, after heating= 

= 2 = (1 − 2 ) ( 5 /2 ) + 22 ( 3 /2 )

= 5 /2 1 () + 1 /2 2 ().

2 − 1 = 1 /2 2 ()

= 1 /2 ∙ 8()

= 4RT