JEE Main201911 Jan 2019Morning ShiftChemistryThermodynamics (C)Actual
Two blocks of the same metal having same mass and at temperature T ₁, and T ₂ , respectively, are brought in contact with each other and allowed to attain thermal equilibrium at constant pressure. The change in entropy, S , for this process is :
Options
- AC _ P [ ( T ₁+ T ₂ )² 4 ~T ₁ ~T ₂ ]
- B2 C_ p [ (T₁+T₂ )^ 1 2 T₁ T₂ ]
- C2 C _ P ( T ₁+ T ₂ 4 ~T ₁ ~T ₂ )
- D2 C _ P [ T ₁+ T ₂ 2 ~T ₁ ~T ₂ ]
Correct answer
A. C _ P [ ( T ₁+ T ₂ )² 4 ~T ₁ ~T ₂ ]
Step-by-step solution
Final temperature = T ₁+ T ₂ 2 , let T ₂> T dS = dq T = C _ p dT T S = C _ p ( T _ f T _ i ) S _ Total = C _ p ( T ₁+ T ₂ 2 ~T ₁ )+ C _ p ( T ₁+ T ₂ 2 ~T ₂ ) = C _ p [ ( T ₁+ T ₂ )² 4 ~T ₁ ~T ₂ ]