Question

A system gains 687 kJ of heat, resulting in a change in internal energy of the system equal to 156 kJ. How much work is done?

1. Work was done by the system.2. Work was done on the system.

Answer 1

w = -531 kJ

1. Work was done by the system.

Step-by-step explanation:

Step 1: Given data

• Heat gained by the system (q): 687 kJ (By convention, when the system absorbs heat, q > 0).

• Change in the internal energy of the system (ΔU°): 156 kJ

Step 2: Calculate the work done (w)

We will use the following expression.

ΔU° = q + w

w = ΔU° - q

w = 156 kJ - 687 kJ

w = -531 kJ

By convention, when w < 0, work is done by the system on the surroundings.