Question

Thomas Midgley invented CFCs as an alternative to ammonia (NH₃) for use in refrigeration. Ammonia gas is flammable and toxic, while CFCs are less toxic and more stable. If the specific heat of NH₃(g) is 2.24 J/(g∗K) and the specific heat of Freon-12 gas is 0.91 J/(g∗K), which substance would be most efficient as a refrigerant? A good refrigerant can absorb heat from its surroundings without its temperature increasing drastically.

A. Freon-12
b. NH₃(g)
c. Cannot be determined with this information

Answer 1

Ammonia (NH₃(g)) is more efficient than Freon-12 as a refrigerant based on its higher specific heat capacity; however, factors like flammability, toxicity, and environmental impact make the less efficient Freon-12 the safer choice, despite being phased out due to ozone depletion concerns.

Step-by-step explanation:

When comparing the efficiency of ammonia (NH₃(g)) and Freon-12 as refrigerants, we consider their specific heat capacities. A good refrigerant should absorb a lot of heat without experiencing a significant increase in temperature. Given that ammonia has a specific heat of 2.24 J/(g∗K) and Freon-12 has a specific heat of 0.91 J/(g∗K), ammonia can absorb more heat per gram for each degree of temperature rise than Freon-12.

Therefore, based on specific heat capacity alone, NH₃(g) would be more efficient as a refrigerant. However, other factors such as flammability and toxicity also play a role in determining the suitability of a refrigerant. While ammonia is more efficient in heat absorption, Freon-12 is less flammable and less toxic, providing a safer alternative. These factors, along with environmental impact, are critical in the choice of refrigerants, with CFCs like Freon-12 now largely replaced due to their ozone-depleting properties.

Answer 2

Ammonia (NH₃) has a higher specific heat capacity than Freon-12, indicating that it could theoretically be more efficient as a refrigerant because it can absorb more heat without its temperature rising significantly. However, Freon-12 was previously preferred over ammonia due to its reduced toxicity and greater stability, despite having a lower specific heat capacity.

Step-by-step explanation:

The question concerns the efficiency of different substances used as refrigerants, specifically ammonia (NH₃) and Freon-12, which is a type of chlorofluorocarbon (CFC). Efficiency in this context refers to the ability of a refrigerant to absorb heat without undergoing a significant increase in temperature, and it is determined by the substance's specific heat capacity. The specific heat capacity is the amount of heat required to raise the temperature of one gram of a substance by one degree Kelvin.

Given that ammonia has a specific heat of 2.24 J/(g*K) and Freon-12 has a specific heat of 0.91 J/(g*K), ammonia can absorb more heat per gram before its temperature rises, compared to Freon-12. Therefore, in terms of specific heat capacity, ammonia (NH₃) would theoretically be more efficient as a refrigerant. However, Freon-12 was created as an alternative to ammonia due to its reduced toxicity and greater stability, not necessarily for its specific heat capacity. It is also noteworthy that CFCs like Freon-12 have been largely phased out due to their damaging effects on the ozone layer.

In conclusion, though ammonia has a higher specific heat capacity, the choice of refrigerant must also consider factors like toxicity, flammability, and environmental impact. Therefore, considering the given information on specific heat capacity alone, the answer to which substance would be most efficient as a refrigerant is ammonia (NH₃).