Question

A system releases 10 kJ of heat and performs 15 kJ of work on the surrounding. Hence the change in internal energy is ______.

Options

• +5 kJ

• −5 kJ

• +25 kJ

• −25 kJ

Answer 1

A system releases 10 kJ of heat and performs 15 kJ of work on the surrounding. Hence the change in internal energy is −25 kJ.

Explanation:

According to the first law of thermodynamics:

ΔU = Q − W

Here, heat is released, so Q = −10 kJ.

Work is done by the system, so W = 15 kJ.

ΔU = −10 − 15

= −25 kJ