GCAP Operator 1 Practice Exam

The correct answer is based on the properties of ammonia (NH3) under saturation conditions. When transitioning from the saturated liquid state to the saturated gas state, a significant amount of heat, known as the latent heat of vaporization, is required to achieve this phase change. For ammonia, this amount is specifically around 561 BTUs per pound.

This heat absorption is necessary to break the intermolecular forces holding the liquid molecules together so that they can enter the gas phase. Under saturated conditions, the ammonia is at equilibrium between its liquid and vapor forms, and adding this amount of heat allows all the liquid to vaporize completely.

The other values listed (144 BTUs, 970 BTUs, and 1 BTU) do not reflect the energy required for this specific phase change of saturated ammonia, indicating that they are either too low or too high in comparison to the known latent heat of vaporization for NH3. The 561 BTUs aligns with established thermodynamic data, confirming it as the accurate figure for this particular transformation of refrigerated ammonia.