Q.

A total of 48 J heat is given to one mole of helium kept in a cylinder. The temperature of helium increases by 2°C. The work done by the gas is (Given: R=8.31 J k-1 mol-1)                 [2024]

1 48 J  
2 23.1 J  
3 24.9 J  
4 72.9 J  

Ans.

(2)   

        Given : ∆Q=48 J

         1st law of thermodynamics, ∆Q=∆U+∆W

          ⇒48=nCv∆T+∆W

           ⇒48=(1)(3R2)(2)+∆W

           ⇒∆W=48-3×R

           ⇒∆W=48-3×(8.3)       

             ⇒∆W=23.1 J