Electrolux (Platen–Munters) absorption refrigerator — working pair and inert gas In an Electrolux refrigerator, identify the correct description of the roles of ammonia, water, and hydrogen within the system.

Introduction / Context:
The Electrolux (Platen–Munters) absorption refrigerator is a heat-powered system using an absorber, generator, and condenser–evaporator arrangement. It avoids mechanical compressors and is widely studied for its elegant thermodynamic design.

Given Data / Assumptions:

• Refrigerant: ammonia (NH3).
• Absorbent: water (H2O).
• Inert gas: hydrogen (H2) to reduce partial pressure of ammonia in the evaporator.

Concept / Approach:
Ammonia is generated from the strong aqua solution in the generator, condensed, throttled to the evaporator, and then evaporated at low temperature. In the evaporator, hydrogen is circulated to lower the partial pressure of ammonia, enabling ammonia to evaporate at a very low temperature even though total pressure remains near ambient. The resulting weak solution returns to the absorber where ammonia is re-absorbed by water.

Step-by-Step Solution:
Identify fluid roles: ammonia = refrigerant, water = absorbent, hydrogen = inert gas in evaporator.In the evaporator, hydrogen dilutes ammonia vapor → reduces ammonia partial pressure.Low partial pressure → ammonia boils at a lower temperature → provides refrigeration.Therefore, the correct statement is that ammonia evaporates in hydrogen.

Verification / Alternative check:
Mass and partial pressure balances in the evaporator show total pressure roughly constant while ammonia’s partial pressure is minimized by hydrogen circulation, matching the observed low evaporating temperature.

Why Other Options Are Wrong:
(a) Ammonia is absorbed in water, not in hydrogen. (b) True elsewhere (absorber) but does not describe the evaporator role asked in the stem. (d) Hydrogen is inert and does not evaporate into ammonia. (e) Water is not the refrigerant in this system.

Common Pitfalls:
Mixing up absorber and evaporator roles; remembering “NH3 in H2 at evaporator, NH3 in H2O at absorber” helps.

Final Answer:
ammonia evaporates in hydrogen