JEE Main2018PhysicsThermodynamicsActual
Two moles of an ideal monoatomic gas occupies a volume V at 27 o C . The gas expands adiabatically to a volume 2 V . Calculate ( a ) the final temperature of the gas and ( b ) change in its internal energy.
Options
- A( a ) 195   K     ( b ) 2.7   kJ
- B( a ) 189   K     ( b ) 2.7   kJ
- C( a ) 195   K     ( b ) - 2.7   kJ
- D( a ) 189   K     ( b ) - 2.7   kJ
Correct answer
D. ( a ) 189   K     ( b ) - 2.7   kJ
Step-by-step solution
T V γ - 1 = C o n s t a n t γ = 5 3 ⇒ 300 V 2 3 = T 2 V 2 3 ⇒ T = 189 K ⇒ Δ U = n C v Δ T = 2 × 3 2 × 8.314 × - 11 = - 2.7   kJ