Correct Option (A)
The assertion (A) states that large cold storage plants utilize ammonia as a refrigerant, whereas domestic refrigerators employ chlorofluorocarbons (CFCs). This statement is factually accurate. Ammonia (NH₃) is preferred in large-scale industrial refrigeration due to its high latent heat of vaporization, excellent heat transfer properties, and lower cost compared to CFCs. CFCs, such as Freon, were historically used in domestic refrigerators due to their non-flammability, low toxicity, and stability, making them suitable for smaller, enclosed systems. However, due to their ozone-depleting potential, CFCs have largely been phased out in favor of alternatives like hydrofluorocarbons (HFCs) and isobutane.
The reason (R) claims that ammonia can be liquefied at ambient temperatures at low pressures. This statement is incorrect. Ammonia has a critical temperature of 132.4 °C and a critical pressure of 113.3 bar. While it can be liquefied at ambient temperatures, it requires significantly high pressures (typically 8-15 bar in refrigeration systems) to do so. Liquefaction at low pressures is not characteristic of ammonia at ambient temperatures.
Therefore, Assertion (A) is true, but Reason (R) is false.
Incorrect Options:
Options 1, 2, and 4 are incorrect because they either incorrectly assess the truthfulness of Assertion (A) or Reason (R), or they incorrectly establish a causal relationship between them. As established, Assertion (A) is true, and Reason (R) is false. Thus, any option suggesting both are true, or that R is true, is incorrect.