Question

1. A system releases 647 kJ of heat and does 125 kJ of work on the surroundings.

What is the change in internal energy of the system (in kJ)?

Answer 1

This given problem based on the first law of thermodynamics which basically telling the conservation of energy.

The mathematical expression is .

Here

= Change in internal energy

which is positive if it is supplied, It is negative if heat is released.

Here because heat is released.

i.e

, It is positive when work done on the system that means work done by the surrounding.

And work done is negative , if work done by the system that means work done on the surrounding.

Now apply the first law of thermodynamics

Hence the change in internal energy is -772KJ.