Psychrometrics terminology:\nThe percentage ratio of a vapor’s partial pressure to the vapor pressure of the pure liquid at the same temperature is called what?

Introduction / Context:
In gas–vapor systems (e.g., humid air), several saturation measures are used. Distinguishing relative saturation from percentage saturation and other humidity metrics is essential for drying calculations, cooling towers, and environmental control.

Given Data / Assumptions:

• Definition refers to partial pressure of vapor (p_v) and saturation vapor pressure at the same temperature (p_v,sat).
• Expressed as a percentage.

Concept / Approach:
relative saturation (%) = 100 * (p_v / p_v,sat) This measure compares how “full” the gas is relative to the maximum vapor pressure at that temperature. Percentage saturation is a different quantity that adjusts for the presence of carrier gas (mole or mass basis) and is typically slightly lower than relative saturation for the same state.

Step-by-Step Solution:
Identify the exact definition in the stem: ratio of partial pressure to saturation pressure at the same temperature.Match with standard term: relative saturation (also commonly called relative humidity for water vapor in air).

Verification / Alternative check:
Psychrometric charts and tables list RH (%) precisely as p_v/p_v,sat × 100 under ideal-gas approximations, which aligns with the definition of relative saturation used in engineering practice.

Why Other Options Are Wrong:
“Percentage saturation” is a distinct measure using humidity ratios; options claiming independence from mixture composition or vapor nature are incorrect—real-gas nonidealities and species identity affect relations; “relative humidity by mass” is nonstandard wording.

Common Pitfalls:
Interchanging relative saturation with percentage saturation; mixing pressure- and humidity-ratio-based definitions.

Final Answer:
relative saturation