How many BTUs are required to convert 1 pound of saturated liquid ammonia to saturated gas?

The correct answer, 561 BTUs, reflects the energy required to convert 1 pound of saturated liquid ammonia to saturated gas at a constant temperature and pressure. This conversion process is known as the latent heat of vaporization, which is the amount of energy needed to change a substance from the liquid phase to the gaseous phase without changing its temperature.

In the case of ammonia, detailed thermodynamic data indicates that the specific latent heat of vaporization is approximately 561 BTUs per pound when transitioning from saturated liquid to saturated gas. This process involves overcoming intermolecular forces that keep the ammonia molecules in the liquid state, thus requiring a significant amount of energy.

The other options do not correspond to the specific latent heat for ammonia under the given conditions, which is critical to understanding why the answer is 561 BTUs.