Question

what limits the amount of work that a system can do?

Explanation:

In thermodynamics, the available energy (exergy) of a system limits the amount of work it can do. Also, factors like internal friction, heat losses to the surroundings, and the second - law of thermodynamics (entropy increase) play a role. Entropy restricts the conversion of heat into work, and losses due to friction and heat transfer reduce the useful work output.

Answer:

The available energy (exergy), internal friction, heat losses, and the second - law of thermodynamics (entropy) limit the amount of work a system can do.