Question

Consider that 168.0 J of work is done on a system and 305.6 J of heat is extracted from the system. In the sense of the first law of thermodynamics, What is the value (including algebraic sign) of W, the work done by the system?

Answer 1

To solve this problem we must resort to the Work Theorem, internal energy and Heat transfer. Summarized in the first law of thermodynamics.

$dQ = dU + dW$

Where,

Q = Heat

U = Internal Energy

By reference system and nomenclature we know that the work done ON the system is taken negative and the heat extracted is also considered negative, therefore

$W = -168J \righarrow$  Work is done ON the system

$Q = -305.6J \rightarrow$ Heat is extracted FROM the system

Therefore the value of the Work done on the system is -158.0J