How much heat must be absorbed to convert 1 pound of saturated NH3 liquid to saturated NH3 gas?

To convert 1 pound of saturated NH3 (ammonia) liquid to saturated NH3 gas, it is important to consider the latent heat of vaporization, which is the amount of heat required to turn a substance from liquid to gas at a constant temperature and pressure.

For ammonia, the latent heat of vaporization is approximately 561 BTUs per pound at its boiling point. This amount of heat is necessary to overcome the intermolecular forces that hold the liquid molecules together, allowing them to escape into the gas phase. When transitioning from saturated liquid to saturated vapor, the temperature remains constant during this phase change, and the heat absorbed is purely for the transformation of state.

Thus, to convert 1 pound of saturated NH3 liquid to saturated NH3 gas, 561 BTUs must be absorbed, making this the correct answer.