Question

A gas can be taken from state a to c by two different reversible processes, a⇒c or a ⇒ b ⇒ c. During the direct process a ⇒ c, 20.0 J of work are done by the system and 30.0 J of heat are added to the system. During the process a ⇒ b ⇒ c, 25.0 J of heat are added to the system. How much work is done by the system during a ⇒ b ⇒ c? 

(A) 5.0 J 

(B) 10.0 J 

(C) 15.0 J 

(D) 20.0 J 

(E) 25.0 J

Answer 1

Correct option (C) 15.0 J

∆U for each process is equal so Q_AC + W_AC = Q_ABC + W_ABC, or +30 J + (–20 J) = +25 J + W_ABC.